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The writing makes little common sense, the numbers are wrong and do not correspond to the graph.
This site has data showing data where the most efficient speed is between about 50kmph and 80kmph, as we would all expect.
https://www.quora.com/By-how-much-does-driving-at-200-km-h-instead-of-100-km-h-increase-the-fuel-consumption/answer/Francois-Dovat?ch=10&share=2aea6204&srid=uehfj — Preceding unsigned comment added by 58.96.70.237 ( talk) 23:49, 16 September 2022 (UTC)
This one shows best is at 80kmph or less:
https://www.greencarcongress.com/2006/05/fuel_consumptio.html
currently, it says: "The power to overcome air resistance increases roughly with the cube of the speed, and thus the energy required per unit distance is roughly proportional to the square of speed" I can see that this is somewhat intuitive as exerting a force that goes like the cube of the speed for a fixed amount of time would mean that you covered more ground the faster you go, but the work done is actually F times X, so the energy required per unit distance is actually linear with the force, and goes like the cube of the speed, not the square! ~~
In this section, the numbers for the 1994 Oldsmobile Cutlass are incorrect. It states that it "gets 2 mpg better economy at 105 km/h (65 mph) than at 72 km/h (45 mph) (9.4 L/100 km (25 mpg-US) vs 5.53 L/100 km (42.5 mpg-US))". Clearly 42.5mpg and 25mpg are not a 2mpg difference.
the conversion between mpg and l/100km is wrong. It should be linear. This graph should be deleted.
The conversion is linear. (the graph looks curved because the vertical axis is 10 times the horizontal, which magnifies the rounding errors)
The function y(x)=235/x is linear by definition. For it to be non-linear, x would need to have an exponent other than one,
e.g. y(x)=235/x^2 or y(x)=235/(x*x).
Confusion arises because mpg is an inverse function of l/100km. So doubling mpg results in l/100km being halved.
Thus, the graph must be removed. It is inaccurate.
[It may be useful to eco-lobbyists but it is still wrong.]
69.159.26.193 (
talk) 19:44, 17 June 2008 (UTC)
Anyone who understands units knows that there is an inverse relationship between mpg and l/100km. Let me explain, mpg is distance (in miles) divided by volume (in gallons), ie, distance/volume. l/100km, on the other hand, is volume (in litres) divided by distance (in 100s of km), ie, volume/distance, hence the inverse relationship between the two, therefore the graph is correct. Derekjc ( talk) 20:50, 13 June 2010 (UTC) Derek Chandler, MEng CEng MIET
The graph is OK, the right shape, and the red and blue are correctly labelled because an imperial gallon is larger, therefore it takes the car for more miles. A graph of y=x is linear (a straight line) with a slope of 1, but a graph of y=1/x has a slope of -1/x^2, so the slope changes from being steep when x is small to gradual when x is large, therefore it's a curve, not a line - in other words, it's nonlinear. That applies also to y=235/x and also any other number divided by x. —Preceding unsigned comment added by 83.143.85.214 ( talk) 13:08, 18 March 2011 (UTC)
The graph should be expanded, not deleted. Right now its in imperial gallons not U.S. gallons and a second curve, with appropriate labels, with US gallons would be very appropriate. Casual users may not read all the graph labels and easily get the wrong conversions (imperial gallons are pretty rare in the U.S. and the rest of the non British world).
Incidentally, the EU standard of 120 g CO2/km translates to about 45.7 mpg [U.S.] or 5.2 L/100km. Which is going to be very tough for them to meet by 2012 since cars normally have a 4-5 year design to production cycle time and only the Prius and Civic hybrids and few small diesels meet that standard now.
Cheers, D'lin ( talk) —Preceding undated comment was added at 06:29, 6 August 2008 (UTC)
Expanded is what I did. The graph is absolutely exact and now includes US and Imperial gallons. -- 85.176.76.85 ( talk) 21:02, 25 July 2009 (UTC)
As far as I can see, the updated graph is mislabeled in that the red upper line should be tagged US MPG while the blue lower line should be Imperial MPG. The US gallon is smaller but the mile is the same (since the 1959 adoption of the international mile anyway) so you burn more US gallons to do the same distance. Chook, Pt Pirie, S. Australia 220.235.117.188 ( talk) 14:05, 25 August 2009 (UTC)
In Drag, is the scaling in consumption per time or consumption per kilometer? Any figure for scaling of consumption per kilometer with speed?
This article will make many people think about substituting their current vehicle. It would be good if a representative figure could be offered for how much energy is wasted in the manufacturing process vs. the lifecycle, so that we don't end up with an increased total energy consumption. —The preceding unsigned comment was added by Alv ( talk • contribs) 07:28, 30 January 2007 (UTC).
The energy content for Gasoline is listed in the first chart as 29 MJ/L, whereas in the Diesel article, it is listed as 34.9. Which is right, if either? NcLean 5th July 2006
29 MJ/L for the energy content of gasoline is inconsistent with the values given in Btu/IGal and Btu/USgal.
Also, the statement made later on in the article about the relative energy content of diesel and gaoline does not agree with this chart. 69.107.90.97 00:25, 1 October 2006 (UTC)
I don't think the tone of the example with a Frenchman and an Englishman is really appropriate. It looks a bit like a school book. Should I change it ? Arsine 21:44, 29 March 2006 (UTC)
If you think you can improve the tone please do so. Be bold! Blaise 22:06, 31 August 2006 (UTC)
Is that example needed at all? Who compares the average consumptions of groups of cars (and very unappropriately grouped by the way - a car that does 3L/100km and one that does 12L/100km. I know it's merely illustrative yet it's not a valid way to judge)? The problem here stems from the arithmetic mean function itself and not the way we express the consumption figures of cars. It may mislead some people to think that they can't compare the consumption figures of two different cars expressed in different units. Again, the fictive comparison of French and English cars is flawed and would be so even without using different units of consumption. Think about a car that consumes 3L and another that consumes 12L. Now on average each one of the cars consume 7,5L, right? Actually neither car consumes that! Let's not forget the shortcomings of mathematical/statistical tools and be careful when interpreting the outcomes.. One must be careful trying to squeeze a lot of information into one or two numbers. ozkaplan 07:21, 21 October 2006 (UTC)
Is it me or is this table inaccurate? For example, Methanol,Etanol etc are shown has having a lower accessible energy content than Gasoline. This is surely upside down in all 4 of the MJ and BTU columns.
Slow acceleration's effect on fuel consumption is greatly overemphasized in North America. Ever since side valve engines disappeared, most engines have had their greatest efficiency at a large fraction of their maximum horsepower. Starting slowly helps much less than stopping slowly, if at all. David R. Ingham 21:33, 23 April 2006 (UTC)
This popular idea may be left over from the age of side valve engines, when more people worried about fuel consumption than now do (Remember gas rationing.), and advocated by people who think that slow acceleration contributes to safety, or it may be a result of the simplified view that the energy is lost when the fuel is burned, rather than when the kinetic energy is converted to heat by the brakes. I suppose it might also be encouraged by the car companies who don't want people to know that it is buying the engine, carrying its weight and size around and keeping it going, not using its full power, that is expensive. The engine uses more fuel when producing more power, but that does not imply that limiting it to a small fraction of its full power achieves an overall reduction in fuel consumption. See "Your Mileage May Differ", Road and Track, May 2006, pp. 105–111. David R. Ingham 05:06, 24 April 2006 (UTC)
Gradual accelaration is not the same as slow accelaration! NcLean 5th July 2006
The most important factor on a modern fuel injection car is keeping the emsisions control in closed loop. As you apply more throttle the ecu will go into open loop (not longer reading the 02 sensor voltage). In open loop control a stock ECU will add extra fuel as a safety margin. In other words the car runs rich at high throttle, this hurts your fuel efficency.
Thegreatms; 1st Aug 2006
Does automatic vs manual transmission make much difference to the importance of low acceleration for fuel efficiency?
I get the impression that the fluid coupling is less efficient at high loads (steep hill, high acceleration, etc.). (I'm not very confident about this.)
Also, I've found that automatic transmissions sometimes change to a lower gear in response to throttle even if doing so actually reduces speed: a lower gear has greater engine speed & friction for a given vehicle speed, which can reduce overall efficiency (or even speed, in extreme cases). Pjrm 07:59, 21 August 2006 (UTC)
A fluid coupling such as a torque converter does wast power by slipping, but modern transmitions lock them out some of the time. (I think this was introduced by Peugeot.) A skillful driver may still be able to do better with a manual, but the difference is decreasing. David R. Ingham 04:41, 30 September 2006 (UTC)
Has anyone had a thought about the history of automobiling, in the technological sense? What is considered as economical now, differs from the idea of economical of the past: Nowadays Engines, fuel and lubrication oil have evolved a lot from what they were in the beginning of the 20th century. By todays standarts, it is economical to drive wasting as little fuel as possible, because (in addition to the enviromental issues) fuel costs a lot. However back in the days of old fuel was cheap, but because engine and lubricating technology was in its birth, building, maintaining and rebuilding engines were heavy for the wallet. Old sidevalve engines, in addition to their poor breathing ability which lowered top end power (~75% at low speeds, ~55% at high speeds, compared to the overheadvalve-engines ~90% and ~75% respectively, if I remember correctly) the engines of old used heavy parts (for example iron pistons were commonplace) and thus the wear and tear was fast when running at high revolutions. This problem was made worse by the combination of long stroke structure and poor lubrication due to oil and engines own lubricating system. However shortstrokers were even worse with their (piston)overheating and predetonation habits, wich made them very unfavorable to the engine manufacturer. This is why the slow acceleration, especially accelerating at low engine speeds, was economical: In those days it was more affordable to use more gasolene, than to cause the engine wear out prematurely. Also large longstrokers were able to pull well at low engine speeds, and as the engines were far less muflled than now, unnecessary noise was avoided.
As I see it, the old way of economical driving comes from those days and has seemingly stayed alive as an urban legend, which are, frankly, seemingly common in the USA. —Preceding unsigned comment added by 84.248.56.90 ( talk) 12:36, 11 January 2008 (UTC)
"Temporarily shifting to neutral on a sufficiently lengthy downhill grade will dramatically increase mileage for carburetor cars, while cars with fuel injection - or carburetor cars with a fuel cut-off solenoid - will benefit more from the fuel cutoff when the car is left in gear."
This is misleading. The friction and compression drag of the engine (its negative efficiency) is much more important that any fuel that is burned while the throttle is closed. How effective this is depends on how much the engine slows the car in highest gear.
(Also, note that it is illegal in some US States.) David R. Ingham 21:41, 23 April 2006 (UTC)
note about the fuel cutoff feature of fuel injection systems: Taking the 25+ year old Bosch Motronic system as an example, the way it works is that the fuel injectors stay closed whenever the throttle is closed and the engine speed is above a certain value (usually in the 1000-2000RPM range depending on the particular model vehicle). It's as simple as that.
This will not save fuel on the highway (except in the case where you would otherwise be using the brakes to stay within a legal speed limit). Depending on the speed one is traveling (and associated drag) and the grade of a hill that one is descending, there are a couple different situations. In the case that shifting into neutral will result in the vehicle losing speed due to drag that the driver will regain by accelerating again shortly after, it is more efficient to leave the car in gear and simply reduce the throttle opening to maintain speed. If shifting into neutral results in the vehicle gaining speed due to gravity, then allowing the vehicle to build speed on the hill and using it to coast some distance after reaching the bottom of the hill before shifting back into gear is the most efficient method.
The fuel cutoff feature is beneficial when the driver intends to reduce speed (ie. coming up to a stop sign) and when the engine is spinning down between upshifts. 69.205.237.124 20:42, 22 September 2007 (UTC)
In addition to the negative efficiency of compression drag, modern fuel-injected engines appear to consume much more fuel when coasting in gear than when idling (although the difference seems to be smaller for engines featuring variable valve timing). At least that is what a fuel consumption meter (such as ScanGauge) which derives data from the Onboard Diagnostic Port indicates. Ad hoc fuel economy measurements over medium length trips also indicate that shifting into neutral on modern fuel-injected cars save noticeable amounts of fuel.
I (the source of the ad hoc measurements mentioned above) regularly drive a couple of specific freeway routes 70-80 miles long where I fill up right before and right after the trip. Of course, I make sure the engine is warm before I fill up the first time, I pay particular attention to my speed (I do drive at different speeds sometimes, but those results go in separate bins), and if I run into significant traffic I obviously ignore the results. I have done this at least ~10 times in a 2004 Civic about 5 times in a 2006 Camry. Usually I put it in neutral at every opportunity, but I have tried not using neutral at least once each car. I feel my results have been pretty consistent. The Civic gets ~50MPG with neutral and ~40 without. The Camry gets ~40MPG with neutral and ~36 without. I believe the difference is bigger for the Civic for 2 reasons: (1) the Civic's tallest gear - 2500RPM @60MPH - is more inefficient than the Camrys 2000RPM @60MPH; (2) the Civic was a manual, so the engine/car speed ratio was locked, whereas the Camry is an automatic, and I've noticed (by looking at the tachometer) its torque converter tends to release a little (lets the engine speed drop about 10%) if you coast in gear for more than a few seconds. But anyway, I've done these experiments enough times to be convinced that neutral saves measurable amounts of gas for my cars. This is not wishful thinking - I would rather have this *not* be the case. I would rather just stay in gear, since messing with neutral worries me in terms of how much life I am taking off of the transmission. 67.170.72.55 22:58, 18 February 2007 (UTC)
(to be clear, I am not disputing the claim that the engine consumes less fuel when coasting in gear than when idling; I am, however, quite convinced based on my experience that coasting in neutral saves fuel overall. I suppose that could be entirely due to engine drag when coasting in gear) 67.170.72.55 22:58, 18 February 2007 (UTC)
I believe the main effect here is engine braking, the work required to pump air through the engine. Downhill, the engine rotates faster in gear and more air is pumped than if it were at idle.
The automatic version of this was called freewheeling, and Saabs had it around 1960. It supposedly increased fuel economy about 15%. It was outlawed because of fears it would lead to runaway cars if it failed to cut out at the same time that brakes failed while descending a long pass, just when engine braking is needed. But decades ago I saw an article (since lost) by an automotive engineer claiming this was wrong: with several independent automatic cutouts -- upon braking, on shifting, manual etc. -- the chance of failure would be astronomically low. Its return would seem to offer an easy way to improve economy and I wish the main article could discuss it. Alan Mole 00:56, 27 February 2007 (UTC)
Well, the "European driving cycle pattern" is not 90 km/h (56 mph) on Motorways, but 120 km/h (75 mph), which is quite worse on economy-aspects (wind drag is much higher). See also NEDC (or for german speaking people a much more extensive description: VDA.de - Unterschiede der Messmethoden) 129.247.247.238 08:13, 1 June 2006 (UTC)
Which condition does the 140 g/km apply to? 5 L/100 km or 6.5 L/100 km? in fact 5 L/100 km is 115 gm CO2/L, while 6.5 is L/100 km is nearer 150 gm/L CO2. In the UK only one mandatory fuel-consumption figure is used to generate a gm/L figure, which is used in the car tax regime. —Preceding unsigned comment added by 82.45.83.254 ( talk) 18:38, 18 March 2011 (UTC)
The note about European driving cycles yielding higher fuel consumption levels than the U.S. cycle needs correction, and the comparison cited, for the Honda CRZ, appears to be comparing the European test results to the U.S. adjusted (for onroad) values, not the actual test results....the U.S. test results will tend to give LOWER fuel consumption levels than the European cycle in most cases. A 2007 ICCT report on fuel economy standards worldwide gave a 1.12 average adjustment factor (multiply European fuel economy test results by 1.12 to get U.S. test results (in mpg or km/L). However, the report also said that the adjustment factors tended to shrink for higher efficiency vehicles.....today, the Honda CRZ has a U.S. test result of about 5.8/4.5 L/100km (city/highway); versus the cited 6.1/4.4 European results...virtually the same. Steve Plotkin Steveneplotkin ( talk) 17:23, 27 March 2013 (UTC)
When highway speed limits and driving behaviors in the United States regularly exceed 50-55mph, the EPA provided information on highway fuel economy is therefore almost useless. The energy required to overcome aerodynamic drag alone over a given distance is 1.4x greater at 65mph and 1.9x greater at 75mph.
The actual fuel economy achieved on highways may therefore actually be worse than those specifications given for "city" driving.
My expectation is that this article will grow too long for a single article as petroleum becomes scarcer and the US comes to its senses about global warming. So if it is merged in now, it might have to be split off again later. David R. Ingham 03:27, 30 September 2006 (UTC)
Fuel efficient driving redirect to this article , but Fuel efficient driving is also in the See Also of this article, just letting you know --shodan
This needs a lot of work. There are various considerations such as idle consumption. Displacement is really not a primary consideration, it is more weight volume and cost. David R. Ingham 03:36, 30 September 2006 (UTC)
I have wondered about this, but the expert that I consulted on this matter did not think this would happen. Turning the key off while moving and in gear will damage engines and catalytic converters of cars that do not shut off the fuel. David R. Ingham 04:12, 30 September 2006 (UTC)
I added a section on this, and an external link to a more detailed discussion of the legislation. KonaScout 00:04, 11 October 2006 (UTC)
Are SUVs and other cars masquerading as trucks exempted?
It would seem simpler and more straightforward to tax fuel. It is always easy to find some other tax to reduce. David R. Ingham 04:30, 15 October 2006 (UTC)
In Turkey there's a %200 tax on fuel, i.e. if oil is 1 USD/liter without tax, it becomes 3 USD/liter with tax. Also annual taxes for cars are based on engine volume and car age, nothing more. i.e. 2 year old car with 1.6 lt engine is taxed at 400 USD / year whereas a 2 year old car with 4.0+ lt engine is taxed at 10,000 USD/year. These two measures greatly discourage the use of large engines, which corresponds to an overall fuel consumption decrease for the country. —Preceding unsigned comment added by 81.213.159.132 ( talk) 08:35, 21 August 2009 (UTC)
This section needs lots of clean-up! Is it a list of devices consumers can install on a car to achieve greater fuel efficiency, or is it technologies that automakers can employ to provide more efficient cars?
Some of these items are scams or hoaxes (magnets, vaporizers, intake air cyclones), which have their own wikipedia page ( http://en.wikipedia.org/wiki/Aftermarket_fuel_economy_device).
The "Quasiturbine" is a type of engine, like the Wankel Rotary engine or the reciprocating four-stroke engine. That in and of itself is not enough to be considered a fuel-saving technology, as one could easily design a Quasiturbine to have greater fuel consumption than an equally powerful conventional engine.
Torque converters "lock" or "lock up", they don't get "locked out."
"Variable Oxygen Sensor Dial"? This needs to be described. Today's oxygen sensors are variable, in that they return a range of voltages corresponding to the amount of oxygen in a car's exhaust.
"EPROM Fuel Computer Chips for leaner burn"? "Lean-burn" is a combustion strategy that can yield higher fuel economy (usually at a high NOx emissions penalty), but EPROM Fuel Computer Chips is gibberish. "EPROM" is a type of computer memory, "Computer Chips" is a generic way to describe computer components, usually processor-related, and sticking the word "Fuel" in the middle is meaningless.
I'm going to make these changes, but I feel more work will need to be done before this section is good to go.
R.Yo 21:19, 11 November 2006 (UTC)
Also, this section is accompanied by a photo of someone riding in a bus powered by charcoal gas. This has nothing to do with fuel economy; this photo should be deleted or moved to an article on alternative fuels. R.Yo 22:06, 11 November 2006 (UTC)
I just did a partial rewrite of the section covering the EPA test methods, as those have been revised as of December 2006 for use on MY2008 vehicles. Additionally, the CAFE standard does not use (and as far as I know, never has used) the EPA fuel economy ratings - so changes in the EPA methods have zero effect on CAFE. Ayocee 14:09, 2 January 2007 (UTC)
Fatter U.S. drivers guzzle more gas, spend extra $2.8 billion annually. -- 217.72.64.8 06:51, 20 January 2007 (UTC)
The title of this article is very childish. How about Automotive fuel economy? X570 06:30, 30 January 2007 (UTC)
Excuse me, but wtf does "MJ/L" "MJ/kg" "BTU/imp" and "BTU/US" mean?!? Was this written by some acronym geek for other acronym geeks? JayKeaton 15:59, 8 February 2007 (UTC)
"While following large transportation vehicles such as trucks or buses can be tedious, on motorways or highways they assist in reducing drag, pushing through the air and leaving your vehicle a large pocket of turbulence to drive behind." Isn't this highly dangerous considering your probably going to have to tail gate that other vechicle so closely to noticeablly reduce drag there's no way you could stop if they hit their breaks sudenly? Jon 18:08, 30 March 2007 (UTC)
Energy Tax Act says the law was passed in 1979, not 1978. Which article is correct? -- Beland 21:04, 16 May 2007 (UTC)
Nempimania & Hypermiler contain about two-three sentences each about the terms in their title. Everything else in both articles is so general that it overlaps considerably with this article. Both should be merged into here. Hypermiler in particular spends more than 3/4 of its length discussing techniques to increase fuel economy, which are mainly dealt with here in a short bulletted list. This article, too, would benefit from the merge. Any objections? MrZaius talk 16:48, 28 May 2007 (UTC)
Governments and environmental organizations urge drivers to adopt driving patterns that minimize their use of fuel, calling them Ecodrivers in Europe, Hypermilers in America, or urging them to obsess to the point of Nepimania in Japan.
Merge completed to Fuel economy maximizing behaviors to prevent it from dominating this article, given the length of the content found in Ecodriving. MrZaius talk 10:03, 3 June 2007 (UTC)
Why is idling not included in this section?-- John of Paris 08:40, 3 June 2007 (UTC)
The article points out that the speed is highly significant for the mileage. But at what speed is an average mileage measured? 90 km/h? --17:54, 16 July 2007 (UTC)
Right now Fuel economy does not exist, it is simply a redirect to Fuel economy in automobiles, this article. There is a separate article Fuel efficiency, which covers the generic issues of fuel economy. 199.125.109.135 06:35, 18 August 2007 (UTC)
"Headlights, media systems, and other electronics do not increase fuel consumption, as the energy to power these devices comes from the charging system; either the alternator or battery."
This is wrong. Putting a higher electrical load on an alternator causes it to take more mechanical energy from the engine via its drive belt. There's no free energy. 69.205.237.124 20:56, 22 September 2007 (UTC)
I started assembling a chart showing actual and required fuel efficiency in various countries, since this information is somewhat scattered about in prose. But we need more numbers for more countries. -- Beland ( talk) 21:41, 4 February 2008 (UTC)
I was reading some news and stumbled upon this article that might provide some useful information for this article. Quite a few facts are presented in this article that might be useful for citations.
"The Good News and Bad News On U.S. Fuel-Economy Trends"
by Joseph B. White
October 1, 2007
Wall Street Journal
URL:
http://online.wsj.com/article/SB119099903267842827.html?mod=hpp_us_personal_journal
Archive URL:
http://www.webcitation.org/5WLHShMhd
Formatted for inline citation: [1]
-- Smiller933 ( talk) 17:19, 15 March 2008 (UTC)
References
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cite web}}
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and |archivedate=
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"Social issues - In Sweden statistical analysis has shown that men do buy less energy efficient cars. The average CO2 emissions for men in Sweden is 184.1 g/km and for women 169.2 g/km (-8.1%).[8]"
Although emissions and fuel mileage are often correlated, they are in no way a function of one another. In other words, higher CO2 doesn't necessarily mean that someone is driving a less energy efficient vehicle. —Preceding unsigned comment added by Daveclark35 ( talk • contribs) 15:37, 5 April 2008 (UTC)
In a related matter, does anyone think that fuel economy should be kept out of the automobile infoboxes? Please voice your opinion at http://en.wikipedia.org/wiki/Template_talk:Infobox_Automobile#Vote_on_Fuel_Economy_in_the_Infobox 198.151.13.8 ( talk) 18:28, 7 May 2008 (UTC)
It is this kind of numerical nonsense that is used by lobbyists and politicians to justify irrational policies.
"switching from a 10 mpg vehicle to a 15 mpg vehicle" allows you to travel 5 miles further on that gallon, a 50% increase.
"switching from a 50 mpg vehicle to a 100 mpg vehicle" gets you 50 miles farther, a 100% increase.
So, the savings in the first case is half that of the second, not 3 times!
Only a deeply entrenched auto executive would try to argue that doubling fuel efficiency (vs half again as much) is a diminishment.
69.159.26.193 (
talk) 20:48, 17 June 2008 (UTC)
I can understand people wanting to use the more familiar (to them) km/l designation. But it is absolutely ridiculous to use km/l in the EPA section of the article. The EPA is an American agency which deals in m.p.g. Hell, you'd be hard pressed to find anyone in the US who has any conception of what km/l really means. —Preceding unsigned comment added by 137.28.228.112 ( talk) 18:19, 5 September 2008 (UTC)
Actually I don't understand the usage of Imperial units. Do all the world other than the Americans and Brits (which is 95% btw) have to search for "what is the corresponding SI unit for this gallon, is it US or imperial gallon..." Correct usage should be lt/100km imo. 81.213.159.132 ( talk) 09:18, 21 August 2009 (UTC)
A petrol (gasoline) engine will produce around 2.32 kg of carbon dioxide for each litre of petrol consumed. Can anyone explain to me how this is possible if a litre of petrol does not even weigh 1 kg??? Shouldn't this be 2.32 grams per litre? (my chemistry knowledge is poor, I admit) Lexw ( talk) 20:59, 17 April 2009 (UTC)
The article is correct. The oxygen in the CO2 weighs far more than the carbon. Greglocock ( talk) 02:02, 18 April 2009 (UTC)
This is true. Petroleum is composed of hydrocarbons pentane to octane. Octane has the chemical formula C8H18, which has an atomic mass of (8*12 + 18 =) 114 g/mol (assuming Carbon is 12 and Hydrogen is 1). CO2 has an atomic weight of (12 + 2*16 =) 44 g/mol (assuming Oxygen is 16). Therefore, assuming the combustion of all 8 carbon atoms, 8 molecules of CO2 has a mass of (8*44 =) 352, which is over three times the mass of the original hydrocarbon. The same is true of all hydrocarbons in petrol; pentane (at the other end of the scale) is C5H12, which has an atomic mass of (5*12 + 12 =) 72 g/mol, but the CO2 produced is (5*44 =) 220. Obviously the mass increase is due to the addition of oxygen, despite the oxidation of hydrogen to water, since hydrogen is the least massive atom, whereas oxygen is 16 times its weight and two atoms of oxygen are joined to each atom of carbon in carbon dioxide. Derekjc ( talk) 21:30, 13 June 2010 (UTC)
27 mpg for the US market? Pretty sure there are a lot of cars with worse mileage than that out there… like, most of the cars on this list. Maybe the average of the whole fleet of an automaker? But what about Ferrari or Hummer, they don't have a single car with such a mileage… or are they counted as Fiat and GM, respectively? The 43 mpg number for China sounds even crazier… Basically there needs to be a lot more sources and explanations for this table, otherwise it's pretty useless. – Kloth ( talk) 18:08, 13 August 2009 (UTC)
The data for the UK fuel economy (or more correct CO2) ratings are incorrect. The correct values follow.
Band | CO2 emission (g/km) |
---|---|
A | Up to 100 |
B | 101-110 |
C | 111-120 |
D | 121-130 |
E | 131-140 |
F | 141-150 |
G | 151-165 |
H | 166-175 |
I | 176-185 |
J | 186-200 |
K* | 201-225 |
L | 226-255 |
M | Over 255 |
These bands are used by the DVLA to determine Vehicle Excuse Duty (aka Road Tax) for cars registered after 1 March 2001; found on the Direct Gov website ( http://www.direct.gov.uk/en/Motoring/OwningAVehicle/HowToTaxYourVehicle/DG_10012524). Derekjc ( talk) 21:53, 13 June 2010 (UTC)
"Fuel economy" is a particular quantity defined by "distance/volume". This general article is about, and should be titled, "Automotive fuel usage" with redirects from "fuel consumption in automobiles and " and "fuel economy in automobiles" —Preceding unsigned comment added by 138.194.37.80 ( talk) 03:09, 21 August 2009 (UTC)
The result of the move request was not moved. Fuel consumption in automobiles has already been redirected here. Jafeluv ( talk) 13:06, 15 September 2009 (UTC)
Fuel economy in automobiles → Fuel_usage_in automobiles — The article is about fuel usage, as measured by the reciprocal quantities "fuel economy" (mpg) and "fuel consumption" (L/100 km). There should be a redirect from "Fuel_economy_in_automobiles" and "Fuel_consumption_in_automobiles" Adamtester ( talk) 06:11, 4 September 2009 (UTC)
The article Miles per gallon needs to be merged into this one. That article is mostly
To the extent that the tables are noteworthy (not sure they are) these can be merged into this article or put in a list article. The rest of it can obviously be merged here. There is no evidence that there is enough that is unique about "miles per gallon" that could be stated to merit a separate article. And regardless, certainly that unique content is not there now.
Dissenting opinions?
-- Mcorazao ( talk) 20:52, 23 May 2010 (UTC)
Good idea Greglocock ( talk) 02:20, 24 May 2010 (UTC)
I'm sort of curious of the sticker pic that say "25 MPG average, expect 21 to 29 in real-world driving".
I'm more used to the fact that numbers quoted by European automakers are hopelessly inflated. That is, converted to US MPGs, my car should make 50 MPG highway, 34 MPG city (European manufacturers' data FWIW). In fact it makes a warm season's average of 29, that's all off-peak city driving. The EPA data for the same engine/transmission/grossweight in a different body style are 40 highway, 29 city - spot on.
Is this a regular pattern (that EPA is closer to real life than Euro-specs) or it is just a random sample?
East of Borschov ( talk) 11:41, 10 June 2010 (UTC)
Hi, I'm too mathematecally stupid to derive this on my own. Could anyone give me a formula to convert the percentage of fuel savings into the percentage of the corresponding mileage gain? Like in, if a new model uses x per cent less fuel than the previous model, by how many per cent does the milage increase?-- Cancun771 ( talk) 06:57, 5 November 2010 (UTC)
Here's a quote from the Gallons per mile section as it currently reads (with a minor typo fixed, the reference removed and the {{convert}} call written out explicitely).
For example, replacing a car that gets 14 mpg-US (17 mpg-imp; 17 L/100 km) with a car that gets 25 mpg-US (30 mpg-imp; 9.4 L/100 km) saves 3 US gallons (2.5 imp gal; 11 L) of fuel every 100 miles (160 km). Because 1 US gallon (0.83 imp gal; 3.8 L) of fuel emits 20 pounds (9.1 kg) of carbon dioxide, saving 3 US gallons (11 L) of fuel every 100 miles (160 km) saves 3 short tons (2.7 t) of carbon dioxide every 10,000 miles (16,000 km) of driving.
Let's look at these conversions. I believe that we would generally agree that conversions should provide readers with a clear and accurate picture of what the original text attempts to illustrate. In order to judge whether this example lives up to this let's filter this text.
Let's first apply an imperial filter. Here's what we'll get.
For example, replacing a car that gets 17 mpg-imp with a car that gets 30 mpg-imp saves 2.5 imp gal of fuel every 100 miles. Because 0.83 imp gal of fuel emits 20 pounds of carbon dioxide, saving 2.5 imperial gallons of fuel every 100 miles saves ??? of carbon dioxide every 10,000 miles of driving.
Now, we should note a potential for rounding error here.
So going from US to imperial the difference in miles per gallon was rounded down but the difference in gallons used per 100 miles was also rounded down. Thus the first of these two rounding errors partially cancells the second such that the total error is about 2.9%. So replacing a car that gets 17 mpg-imp with a car that gets 30 mpg-imp actually does save 2.5 imp gal of fuel every 100 miles.
100 mi ÷ 17 mpg-imp = 5+15⁄17 imp gal
100 mi ÷ 30 mpg-imp = 3+1⁄3 imp gal
This gives a difference of 2+28⁄51 imp gal, which is approximately 2.5 imp gal. Thus, all's well so far when we look through our imperial filter.
But now we come across this. "0.83 imp gal of fuel emits 20 pounds of carbon dioxide". Why in the world would we be considering how much CO
2 is emitted when 0.83 imp gal of fuel is burnt? What kind of number is 0.83? This is what I'm calling a "misconversion". The original ratio was "20 lb/US gal" and we converted the wrong part. "20 lb/0.83 imp gal" is pure nonsense imparting very little understanding to our imperial-minded readers. The sensible conversion is, of course, "24 lb/imp gal".
How much does this amount to in tons of CO
2 per 10,000 miles, then? 3 short tons ... short tons ... ? Wait a minute ... 2.7 tonnes ... what happened to the conversion to imperial? If we're going to bother with imperial gallons, we ought to bother with imperial tons i.e. long tons. So we should convert these 3 short tons into long tons ... but wait.
Compare these:
1. "Replacing car 1 with car 2 saves 3 US gal/100 mi. Saving 3 US gal/100 mi saves 3 short tons per 10,000 mi."
2. "Replacing car 1 with car 2 saves 3 US gal/100 mi, this entails a saving of 3 short tons per 10,000 mi."
Number 2 is more concise but there is a more subtle difference. Number 1 says "Saving 3 US gal/100 mi saves 3 short tons per 10,000 mi." whereas number 2 implies "Replacing car 1 with car 2 saves 3 short tons per 10,000 mi."
Saving 3 US gal/100 mi does indeed save 3 short tons per 10,000 miles which is equal to a saving of 2.7 long tons per 10,000 miles. However, remember that the 3 US gal/100 mi figure was an approximation in the first place. How many long tons are we saving by replacing car 1 with car 2? Well, replacing the 14 mpg-US with the 25 mpg-US car actually saved us 3+1⁄7 US gal/100 mi which saves us 3+1⁄7 short tons per 10,000 miles which is actually 2.806 long tons per 10,000 miles (to four sig figs) rather than 2.7. But what about the (slightly different) 17 mpg-imp vs 30 mpg-imp cars? As with the previous calculation, the errors partially cancel leaving no difference when rounded to two significant figures.
Thus it's still accurate to say the following.
For example, replacing a car that gets 17 mpg-imp with a car that gets 30 mpg-imp saves 2.5 imperial gallons of fuel every 100 miles. Because the combustion of 1 imperial gallon of fuel emits 24 pounds of carbon dioxide, this will save 2.7 long tons of carbon dioxide every 10,000 miles of driving.
I think therefore, we could justify the following.
For example, replacing a car that gets 14 mpg-US (17 mpg-imp) with a car that gets 25 mpg-US (30 mpg-imp) saves 3 US gallons (2.5 imp gal) of fuel every 100 miles. Because the combustion of 1 US gallon of fuel emits 20 pounds of carbon dioxide (1 imp gal emits 24 lb), this saves 3 short tons (2.7 long tons) of carbon dioxide every 10,000 miles of driving.
But now let's apply our metric filter. This is where the fun really begins.
For example, replacing a car that uses 17 L/100 km with a car that uses 9.4 L/100 km saves 11 L of fuel every 160 km. Because 3.8 L of fuel emits 9.1 kg of carbon dioxide, saving 11 L of fuel every 160 km saves 2.7 t of carbon dioxide every 16,000 km of driving.
Not really, replacing a car that uses 17 L/100 km with a car that uses 9.4 L/100 km saves 7.6 L/100 km which is 12.16 L/160 km not 11 L/160 km. So, it's not accurate at all, there an approximate 11% error here. But wait ... why ... oh, why are we talking litres per 160 km? What's the significance of this number 160? None. In the metric world, none at all. Here again is what I'm calling misconversion. A conversion from US gallons per hundred miles to litres per hundred miles is as useful as windscreen wipers on a submarine. This is not a conversion to metric, it's a conversion to mongrel. Further, what kind of example is this? Replacing a car that uses 17 L/100 km with a car that uses 9.4 L/100 km? Why choose such a number as 9.4 for an example? Why not a nice round number like 9 or 10?
Next, "3.8 L of fuel emits 9.1 kg of carbon dioxide" ... how many litres? Is there anything special about 3.8? Here's another misconversion. 20 pounds per US gallon is 2.4 kilograms per litre. "9.1 kilograms per 3.8 litres" is rubbish. More rubbish follows with 2.7 tonnes per 16,000 kilometres. What's the sense in a conversion to tonnes per 16,000 km? We want tonnes per 10,000 km.
How can we rescue this example? We might like to round 9.4 down to 9. The we're saving 8 L/100 km. This saves us 1.917 t of CO
2 per 10,000 kilometres. But 3 short tons per 10,000 miles is 1.691 t/10,000 km. Rounding up to 10 would give 1.678 t/10,000 km so we could accurately say "3 short tons per 10,000 miles (1.7 t/10,000 km)" but "25 mpg-US (10 L/100 km)" would not be valid. Perhaps the best thing would be to split the example up like this.
For example, replacing a car that gets 14 mpg-US (17 mpg-imp) with a car that gets 25 mpg-US (30 mpg-imp) saves 3 US gallons (2.5 imp gal) of fuel every 100 miles. Because 1 US gallon of fuel emits 20 pounds of carbon dioxide (1 imp gal emits 24 lb and 1 L emits 2.4 kg), this saves 3 short tons (2.7 long tons) of carbon dioxide every 10,000 miles of driving. Similarly, replacing a car that uses 17 L/100 km with a car that uses 10 L/100 km saves 7 L of fuel every 100 km. This represents a saving of 1.7 t of carbon dioxide every 10,000 km of driving.
But was there anything special about 14 mpg-US and 25 mpg-US in the first place? What about choosing different numbers? How about 16 mpg-US and 30 mpg-US? 16 mpg-US is about 19.215 mpg-imp or 14.701 L/100 km. 30 mpg-US is about 36.028 mpg-imp or 7.840 L/100 km. Now for a little rounding off and we're replacing a car that gets 16 mpg-US (19 mpg-imp or 15 L/100 km) with a car that gets 30 mpg-US (36 mpg-imp or 8 L/100 km).
So 16 mpg-US → 30 mpg-US still saves about 3 US gal per 100 mi, 19 mpg-imp → 36 mpg-imp still saves about 2.5 im gal per 100 mi and we've now got a nice round 7 L/100 km. So we could reword the whole thing like this.
For example, replacing a car that gets 16 mpg-US (19 mpg-imp or 15 L/100 km) with a car that gets 30 mpg-US (36 mpg-imp or 8 L/100 km) saves 3 US gallons (2.5 imp gal) of fuel every 100 miles (7 L/100 km). Because the combustion of 1 US gallon of fuel emits 20 pounds of carbon dioxide (burning 1 imp gal emits 24 lb and burning 1 L emits 2.4 kg), this saves 3 short tons (2.7 long tons) of carbon dioxide every 10,000 miles (1.7 t every 10,000 km) of driving.
JIMp talk· cont 08:22, 7 August 2011 (UTC)
It seems to me the entire "Units of measure" section is needlessly complicated and laden with so much alphabet soup that it does more to confuse the issue than explain it.
This may spring from my ignorance of the field, but, describing fuel consumption and fuel economy as two different things ("fuel per distance" and "input per output") seems absurd. Both measure exactly the same thing - the relationship of fuel consumed to distance traveled. It's just a question of which unit is in the numerator. Why not state this as "fuel per unit distance" and "distance per unit fuel"? This would make the inverse proportionality more intuitively clear to the reader.
Likewise, much of this section is bogged down in unit conversions - would it work better if the table at the end of the "Gallons per mile" section was higher up, and the discussion of the math stuck to a single unit?
Finally, the "Inverse or reciprocal scale" section seems to make the argument that one measurement is better than the other for comparing the fuel efficiency of automobiles. Again, they both measure the same thing, and the mathematical operation to compare them (dividing one by the other) will give the same result.
10 MPG = 0.1 GPM
20 MPG = 0.05 GPM
20 MPG / 10 MPG = 2, an improvement by a factor of 2.
0.1 GPM / 0.05 GPM = 2, an improvement by a factor of 2.
You have to flip the division order, because you've flipped the units; however, even if you don't, you're going to get the proportionality constant (or its reciprocal) out. It's the same number because by finding the factor of improvement, you cancel out the units. The consumer confusion mentioned in this section seems not to be due to the inverse relationship (as it claims), but because consumers are comparing the numbers by looking at the difference in values, rather than the factor between them.
I didn't want to make any changes (I know a lot more about manipulating units than I do about cars), but hopefully this will draw more informed editors' attention to the confusing nature of the section. I came across this page today, and spent a good 10-15 minutes trying to decipher what it was trying to convey, and I teach general chemistry - I fiddle with these types of unit conversions every day. I can't imagine how confusing it would be to the average consumer.
Of course, if my thinking is way off base here (entirely a possibility) please feel free to correct me. Thanks! StellarFury ( talk) 00:02, 10 December 2011 (UTC)
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The article correctly says that L/100km is the measure of fuel economy used in Australia, New Zealand and South Africa. However, the diagram says "MPG to l/100km conversion chart: blue: US gal, red: imp gal (UK and British commonwealth)"
This is wrong in several ways:
To remedy this inaccuracy, I suggest the following change:
I also suggest spelling out the words for greater ease of reading. Michael Glass ( talk) 13:50, 10 February 2013 (UTC)
Diagram label changed as proposed. Michael Glass ( talk) 21:51, 11 February 2013 (UTC)
I have noticed that the article frequently uses a lower case l as a symbol for litre. The BIPM allows both the lower case l and the upper case, but it notes that the lower case l is liable to be confused with the numeral 1 See the BIPM brochure (PDF), page 38. I therefore propose that the the upper case L be used consistently throughout the article.
Are there any comments or concerns? Michael Glass ( talk) 21:48, 11 February 2013 (UTC)
I have moved HCCI from the section Engine combustion strategies to the section Future technologies. No-one is in production with HCCI as of Jan 2014, and I'm not sure it will happen as soon as proposed by some OEMs either. Mike163 ( talk) 17:02, 17 January 2014 (UTC)
Following text (taken from the old Low-energy vehicle page) can be added to the fuel efficiency statistics page;
Higher efficiency can be achieved by changing the vehicle's design, and/or by modifying its powertrain. Energy consumption as low as 5-12.5 kWh/100 km (180-450 kJ/km) is achieved directly by battery electric microcars. When comparing the efficiency of electric cars with IC cars the efficiency of the power generation has to be considered, for example the distribution efficiency for Europe is about 40%, [1] so the overall energy consumption of electric cars lies in the range 0.45 to 1.1 MJ/km. (Average energy efficiency of US plants 33% US DOE (ref to follow) US grid transmission loss 9.5%, UK grid transmission loss 7.4 (ref Wikipedia national grid entry) - transmission losses not included in electric car efficiency figure.) By the year 2050, consumption levels of 1.6 l/100 km (0.64 MJ/km) in diesel-fuelled cars and 2 l/100 km (0.7 MJ/km) in petrol-fuelled cars are deemed feasible. [2] The energy consumption figures for petrol and diesel cars also need to be increased by 18% [3] to represent the oil used in processing and distributing oil-based fuel, to 0.75 MJ/km for diesel, and 0.82 MJ/km for petrol.
To put these consumption figures into perspective a consumption of 1000 km/litre (2350 mpg US) is 0.0344 MJ/km, excluding distribution energy. At 20 km/h it would take 50 hours to travel 1000 km, so with a 20% efficient internal combustion engine it would need to attain and keep this speed using just 38.2 watts.
Even one of the most fuel efficient two seater on the market - the Smart MHD- consumes two or three times more energy per km than a cabin based ultralight two seater would - proven by the 1l prototype by VW. Pilot vehicles have proven that a feasible target may lie in the range of 1-2 l/100 km, or lower, or 10 kWh/100 km electricity. Available electric LEVs already use substantially less energy than available cars, e.g. 4–8 kW·h/100 km for the Twike,. [4] Here the challenges are increasing range and lifetime of batteries, crash worthiness, passenger comfort, performance and reducing the price (which is currently about twice that of a cheap conventional four seater).
Energy Efficiency in MJ per km or kWh per 100 km: It is more straightforward to express energy efficiency in MJ (Mega-Joule) per km because terms like MPG (Miles Per Gallon) and litres per 100 km do not take into account what type of fuel is used and thus the numbers will be distorted for different fuel types. Diesel contains 38.7MJ per litre, Gasoline 34.6MJ per litre and Bio-Diesel 30.5MJ per litre, whereas LPG contains only 22.2MJ per liter which is why the number of litres consumed go up drastically when converting a gasoline car to LPG. This does not mean that the energy consumption goes up; it only means that there is less energy in a litre of LPG. Ethanol also contains much less energy per litre than gasoline. To compare electricity and gasoline its easier to use kWh/100 km since 1l gasoline holds around 10kWh.
Energy demand may be kept low by:
Technological support for low energy operation may also come from driver assistance systems since driving style can be adapted to achieve lower energy consumption. Energy management becomes possible with hybrid vehicles with the possibility to recuperate braking energy and to operate the internal combustion engine (ICE) at higher efficiency on average. Hybrid power trains may also reduce the ICE-engine size thus increasing the average load factor and minimising the part load losses. Purely electric vehicles use up to 10 x less energy (0,3 to 0,5MJ/km) than those with combustion engines (3 to 5MJ/km and up to 10MJ/km for SUVs) because of the much higher motor and battery efficiencies.
Average data for vehicle types sold in the U.S.A. [7]:
Type | Width | Height | Curb weight | Combined fuel economy | Percent | Occupancy rate 2005 Florida [8] |
---|---|---|---|---|---|---|
SUVs | 73.5 in 187 cm | 70.7 in 180 cm | 4242 lb 1924 kg | 19.19 mpg 12.25 l/100 km | 328% | |
Minivans | 75.9 in 193 cm | 70.2 in 178 cm | 4275 lb 1939 kg | 20.36 mpg 11.55 l/100 km | 309% | 1.67 |
Family sedans | 70.3 in 179 cm | 57.3 in 146 cm | 3144 lb 1426 kg | 26.94 mpg 8.73 l/100 km | 234% | 1.35 |
Toyota Prius | 66.7 in 169 cm | 57.6 in 146 cm | 2765 lb 1254 kg | 56 mpg 4.2 l/100 km | 112% | n.a |
GM Volt | 70.8 in 180 cm | 56.3 in 143 cm | 3790 lb 1720 kg | 60 mpg 4.0 l/100 km | 105% | n.a. |
Honda Insight [9] | 66.7 in 169 cm | 53.3 in 135 cm | 1850 lb 839 kg | 63 mpg 3.73 l/100 km | 100% | n.a. |
Audi A2 | 65.9 in 167 cm | 61.1 in 155 cm | 1973 lb 895 kg | 71 mpg 3.0 l/100 km | 81% | n.a. |
The drag resistance for an SUV, compared with a family sedan with the same drag coefficient, is approximately 30% higher, and its increased mass means that the acceleration forces has to be 35% bigger for a given acceleration. This gives a 40% increase in fuel consumption. The last column in the table demonstrates that with the exception of the Prius and the pick-ups all the alternatives have roughly the same potential fuel usage per passenger IF they were fully occupied. However the fuel usage per passenger really depends on the occupancy rate of each type. In 2000 the occupancy rate was only 1.6 in practice, decreasing each year, averaged across all vehicle types and journey types, [10] and 1.2 for commuting.
The fuel consumption of an engine is depicted as a 3dimensional map where the consumption is shown against RPM and torque. Normally the smallest consumption is seen in the upper middle part of the diagram. For diesel engines this region is bigger to lower torque and extends to higher RPM. The choice of engine power for a given vehicle should consider the typical application - for non transient low velocity operation this leads to lower power requirements, at the cost of reduced acceleration and top speed. A hybrid electric concept allows an even lower power internal combustion engine, but the added weight pays only off if operating in stop and go conditions frequently or generally at low power, if using a series hybrid electric concept.
The EU- sponsored RECODRIVE project [11] has set up a quality circle to manage low energy consumption in fleets. This starts with energy aware procurement, and includes fuel management, driver information and training and incentives for all staff involved in the fleet management and maintenance process. Vehicle equipped with gear shift indicators, tire pressure monitoring systems and downsized internal combustion engines and for stop'n go operation also hybrid electric power trains will help to save fuel.
KVDP ( talk) 12:20, 11 February 2014 (UTC)
References
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I'd like to propose some changes to this article, mostly regarding restructuring for better readability and flow:
I've got a version of my proposed edits in my sandbox here, and given my COI, I'm happy to collaborate and discuss any concerns or the merits of these suggestions and make changes accordingly before submitting an edit request. FacultiesIntact ( talk) 23:30, 23 March 2015 (UTC)
THS was based on a vehicle built at TRW by Dr. Baruch Berman, Dr. George H. Gelb and Dr. Neal A. Richardson in 1971 so Toyota is NOT the inventor of series/parallel hybrids. Greglocock ( talk) 12:37, 18 July 2015 (UTC)
Hi. FYI the "experimental car" from 1916 pictured is a production car, see this article
Rolling Phantom ( talk) 21:00, 23 June 2016 (UTC)
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The writing makes little common sense, the numbers are wrong and do not correspond to the graph.
This site has data showing data where the most efficient speed is between about 50kmph and 80kmph, as we would all expect.
https://www.quora.com/By-how-much-does-driving-at-200-km-h-instead-of-100-km-h-increase-the-fuel-consumption/answer/Francois-Dovat?ch=10&share=2aea6204&srid=uehfj — Preceding unsigned comment added by 58.96.70.237 ( talk) 23:49, 16 September 2022 (UTC)
This one shows best is at 80kmph or less:
https://www.greencarcongress.com/2006/05/fuel_consumptio.html
currently, it says: "The power to overcome air resistance increases roughly with the cube of the speed, and thus the energy required per unit distance is roughly proportional to the square of speed" I can see that this is somewhat intuitive as exerting a force that goes like the cube of the speed for a fixed amount of time would mean that you covered more ground the faster you go, but the work done is actually F times X, so the energy required per unit distance is actually linear with the force, and goes like the cube of the speed, not the square! ~~
In this section, the numbers for the 1994 Oldsmobile Cutlass are incorrect. It states that it "gets 2 mpg better economy at 105 km/h (65 mph) than at 72 km/h (45 mph) (9.4 L/100 km (25 mpg-US) vs 5.53 L/100 km (42.5 mpg-US))". Clearly 42.5mpg and 25mpg are not a 2mpg difference.
the conversion between mpg and l/100km is wrong. It should be linear. This graph should be deleted.
The conversion is linear. (the graph looks curved because the vertical axis is 10 times the horizontal, which magnifies the rounding errors)
The function y(x)=235/x is linear by definition. For it to be non-linear, x would need to have an exponent other than one,
e.g. y(x)=235/x^2 or y(x)=235/(x*x).
Confusion arises because mpg is an inverse function of l/100km. So doubling mpg results in l/100km being halved.
Thus, the graph must be removed. It is inaccurate.
[It may be useful to eco-lobbyists but it is still wrong.]
69.159.26.193 (
talk) 19:44, 17 June 2008 (UTC)
Anyone who understands units knows that there is an inverse relationship between mpg and l/100km. Let me explain, mpg is distance (in miles) divided by volume (in gallons), ie, distance/volume. l/100km, on the other hand, is volume (in litres) divided by distance (in 100s of km), ie, volume/distance, hence the inverse relationship between the two, therefore the graph is correct. Derekjc ( talk) 20:50, 13 June 2010 (UTC) Derek Chandler, MEng CEng MIET
The graph is OK, the right shape, and the red and blue are correctly labelled because an imperial gallon is larger, therefore it takes the car for more miles. A graph of y=x is linear (a straight line) with a slope of 1, but a graph of y=1/x has a slope of -1/x^2, so the slope changes from being steep when x is small to gradual when x is large, therefore it's a curve, not a line - in other words, it's nonlinear. That applies also to y=235/x and also any other number divided by x. —Preceding unsigned comment added by 83.143.85.214 ( talk) 13:08, 18 March 2011 (UTC)
The graph should be expanded, not deleted. Right now its in imperial gallons not U.S. gallons and a second curve, with appropriate labels, with US gallons would be very appropriate. Casual users may not read all the graph labels and easily get the wrong conversions (imperial gallons are pretty rare in the U.S. and the rest of the non British world).
Incidentally, the EU standard of 120 g CO2/km translates to about 45.7 mpg [U.S.] or 5.2 L/100km. Which is going to be very tough for them to meet by 2012 since cars normally have a 4-5 year design to production cycle time and only the Prius and Civic hybrids and few small diesels meet that standard now.
Cheers, D'lin ( talk) —Preceding undated comment was added at 06:29, 6 August 2008 (UTC)
Expanded is what I did. The graph is absolutely exact and now includes US and Imperial gallons. -- 85.176.76.85 ( talk) 21:02, 25 July 2009 (UTC)
As far as I can see, the updated graph is mislabeled in that the red upper line should be tagged US MPG while the blue lower line should be Imperial MPG. The US gallon is smaller but the mile is the same (since the 1959 adoption of the international mile anyway) so you burn more US gallons to do the same distance. Chook, Pt Pirie, S. Australia 220.235.117.188 ( talk) 14:05, 25 August 2009 (UTC)
In Drag, is the scaling in consumption per time or consumption per kilometer? Any figure for scaling of consumption per kilometer with speed?
This article will make many people think about substituting their current vehicle. It would be good if a representative figure could be offered for how much energy is wasted in the manufacturing process vs. the lifecycle, so that we don't end up with an increased total energy consumption. —The preceding unsigned comment was added by Alv ( talk • contribs) 07:28, 30 January 2007 (UTC).
The energy content for Gasoline is listed in the first chart as 29 MJ/L, whereas in the Diesel article, it is listed as 34.9. Which is right, if either? NcLean 5th July 2006
29 MJ/L for the energy content of gasoline is inconsistent with the values given in Btu/IGal and Btu/USgal.
Also, the statement made later on in the article about the relative energy content of diesel and gaoline does not agree with this chart. 69.107.90.97 00:25, 1 October 2006 (UTC)
I don't think the tone of the example with a Frenchman and an Englishman is really appropriate. It looks a bit like a school book. Should I change it ? Arsine 21:44, 29 March 2006 (UTC)
If you think you can improve the tone please do so. Be bold! Blaise 22:06, 31 August 2006 (UTC)
Is that example needed at all? Who compares the average consumptions of groups of cars (and very unappropriately grouped by the way - a car that does 3L/100km and one that does 12L/100km. I know it's merely illustrative yet it's not a valid way to judge)? The problem here stems from the arithmetic mean function itself and not the way we express the consumption figures of cars. It may mislead some people to think that they can't compare the consumption figures of two different cars expressed in different units. Again, the fictive comparison of French and English cars is flawed and would be so even without using different units of consumption. Think about a car that consumes 3L and another that consumes 12L. Now on average each one of the cars consume 7,5L, right? Actually neither car consumes that! Let's not forget the shortcomings of mathematical/statistical tools and be careful when interpreting the outcomes.. One must be careful trying to squeeze a lot of information into one or two numbers. ozkaplan 07:21, 21 October 2006 (UTC)
Is it me or is this table inaccurate? For example, Methanol,Etanol etc are shown has having a lower accessible energy content than Gasoline. This is surely upside down in all 4 of the MJ and BTU columns.
Slow acceleration's effect on fuel consumption is greatly overemphasized in North America. Ever since side valve engines disappeared, most engines have had their greatest efficiency at a large fraction of their maximum horsepower. Starting slowly helps much less than stopping slowly, if at all. David R. Ingham 21:33, 23 April 2006 (UTC)
This popular idea may be left over from the age of side valve engines, when more people worried about fuel consumption than now do (Remember gas rationing.), and advocated by people who think that slow acceleration contributes to safety, or it may be a result of the simplified view that the energy is lost when the fuel is burned, rather than when the kinetic energy is converted to heat by the brakes. I suppose it might also be encouraged by the car companies who don't want people to know that it is buying the engine, carrying its weight and size around and keeping it going, not using its full power, that is expensive. The engine uses more fuel when producing more power, but that does not imply that limiting it to a small fraction of its full power achieves an overall reduction in fuel consumption. See "Your Mileage May Differ", Road and Track, May 2006, pp. 105–111. David R. Ingham 05:06, 24 April 2006 (UTC)
Gradual accelaration is not the same as slow accelaration! NcLean 5th July 2006
The most important factor on a modern fuel injection car is keeping the emsisions control in closed loop. As you apply more throttle the ecu will go into open loop (not longer reading the 02 sensor voltage). In open loop control a stock ECU will add extra fuel as a safety margin. In other words the car runs rich at high throttle, this hurts your fuel efficency.
Thegreatms; 1st Aug 2006
Does automatic vs manual transmission make much difference to the importance of low acceleration for fuel efficiency?
I get the impression that the fluid coupling is less efficient at high loads (steep hill, high acceleration, etc.). (I'm not very confident about this.)
Also, I've found that automatic transmissions sometimes change to a lower gear in response to throttle even if doing so actually reduces speed: a lower gear has greater engine speed & friction for a given vehicle speed, which can reduce overall efficiency (or even speed, in extreme cases). Pjrm 07:59, 21 August 2006 (UTC)
A fluid coupling such as a torque converter does wast power by slipping, but modern transmitions lock them out some of the time. (I think this was introduced by Peugeot.) A skillful driver may still be able to do better with a manual, but the difference is decreasing. David R. Ingham 04:41, 30 September 2006 (UTC)
Has anyone had a thought about the history of automobiling, in the technological sense? What is considered as economical now, differs from the idea of economical of the past: Nowadays Engines, fuel and lubrication oil have evolved a lot from what they were in the beginning of the 20th century. By todays standarts, it is economical to drive wasting as little fuel as possible, because (in addition to the enviromental issues) fuel costs a lot. However back in the days of old fuel was cheap, but because engine and lubricating technology was in its birth, building, maintaining and rebuilding engines were heavy for the wallet. Old sidevalve engines, in addition to their poor breathing ability which lowered top end power (~75% at low speeds, ~55% at high speeds, compared to the overheadvalve-engines ~90% and ~75% respectively, if I remember correctly) the engines of old used heavy parts (for example iron pistons were commonplace) and thus the wear and tear was fast when running at high revolutions. This problem was made worse by the combination of long stroke structure and poor lubrication due to oil and engines own lubricating system. However shortstrokers were even worse with their (piston)overheating and predetonation habits, wich made them very unfavorable to the engine manufacturer. This is why the slow acceleration, especially accelerating at low engine speeds, was economical: In those days it was more affordable to use more gasolene, than to cause the engine wear out prematurely. Also large longstrokers were able to pull well at low engine speeds, and as the engines were far less muflled than now, unnecessary noise was avoided.
As I see it, the old way of economical driving comes from those days and has seemingly stayed alive as an urban legend, which are, frankly, seemingly common in the USA. —Preceding unsigned comment added by 84.248.56.90 ( talk) 12:36, 11 January 2008 (UTC)
"Temporarily shifting to neutral on a sufficiently lengthy downhill grade will dramatically increase mileage for carburetor cars, while cars with fuel injection - or carburetor cars with a fuel cut-off solenoid - will benefit more from the fuel cutoff when the car is left in gear."
This is misleading. The friction and compression drag of the engine (its negative efficiency) is much more important that any fuel that is burned while the throttle is closed. How effective this is depends on how much the engine slows the car in highest gear.
(Also, note that it is illegal in some US States.) David R. Ingham 21:41, 23 April 2006 (UTC)
note about the fuel cutoff feature of fuel injection systems: Taking the 25+ year old Bosch Motronic system as an example, the way it works is that the fuel injectors stay closed whenever the throttle is closed and the engine speed is above a certain value (usually in the 1000-2000RPM range depending on the particular model vehicle). It's as simple as that.
This will not save fuel on the highway (except in the case where you would otherwise be using the brakes to stay within a legal speed limit). Depending on the speed one is traveling (and associated drag) and the grade of a hill that one is descending, there are a couple different situations. In the case that shifting into neutral will result in the vehicle losing speed due to drag that the driver will regain by accelerating again shortly after, it is more efficient to leave the car in gear and simply reduce the throttle opening to maintain speed. If shifting into neutral results in the vehicle gaining speed due to gravity, then allowing the vehicle to build speed on the hill and using it to coast some distance after reaching the bottom of the hill before shifting back into gear is the most efficient method.
The fuel cutoff feature is beneficial when the driver intends to reduce speed (ie. coming up to a stop sign) and when the engine is spinning down between upshifts. 69.205.237.124 20:42, 22 September 2007 (UTC)
In addition to the negative efficiency of compression drag, modern fuel-injected engines appear to consume much more fuel when coasting in gear than when idling (although the difference seems to be smaller for engines featuring variable valve timing). At least that is what a fuel consumption meter (such as ScanGauge) which derives data from the Onboard Diagnostic Port indicates. Ad hoc fuel economy measurements over medium length trips also indicate that shifting into neutral on modern fuel-injected cars save noticeable amounts of fuel.
I (the source of the ad hoc measurements mentioned above) regularly drive a couple of specific freeway routes 70-80 miles long where I fill up right before and right after the trip. Of course, I make sure the engine is warm before I fill up the first time, I pay particular attention to my speed (I do drive at different speeds sometimes, but those results go in separate bins), and if I run into significant traffic I obviously ignore the results. I have done this at least ~10 times in a 2004 Civic about 5 times in a 2006 Camry. Usually I put it in neutral at every opportunity, but I have tried not using neutral at least once each car. I feel my results have been pretty consistent. The Civic gets ~50MPG with neutral and ~40 without. The Camry gets ~40MPG with neutral and ~36 without. I believe the difference is bigger for the Civic for 2 reasons: (1) the Civic's tallest gear - 2500RPM @60MPH - is more inefficient than the Camrys 2000RPM @60MPH; (2) the Civic was a manual, so the engine/car speed ratio was locked, whereas the Camry is an automatic, and I've noticed (by looking at the tachometer) its torque converter tends to release a little (lets the engine speed drop about 10%) if you coast in gear for more than a few seconds. But anyway, I've done these experiments enough times to be convinced that neutral saves measurable amounts of gas for my cars. This is not wishful thinking - I would rather have this *not* be the case. I would rather just stay in gear, since messing with neutral worries me in terms of how much life I am taking off of the transmission. 67.170.72.55 22:58, 18 February 2007 (UTC)
(to be clear, I am not disputing the claim that the engine consumes less fuel when coasting in gear than when idling; I am, however, quite convinced based on my experience that coasting in neutral saves fuel overall. I suppose that could be entirely due to engine drag when coasting in gear) 67.170.72.55 22:58, 18 February 2007 (UTC)
I believe the main effect here is engine braking, the work required to pump air through the engine. Downhill, the engine rotates faster in gear and more air is pumped than if it were at idle.
The automatic version of this was called freewheeling, and Saabs had it around 1960. It supposedly increased fuel economy about 15%. It was outlawed because of fears it would lead to runaway cars if it failed to cut out at the same time that brakes failed while descending a long pass, just when engine braking is needed. But decades ago I saw an article (since lost) by an automotive engineer claiming this was wrong: with several independent automatic cutouts -- upon braking, on shifting, manual etc. -- the chance of failure would be astronomically low. Its return would seem to offer an easy way to improve economy and I wish the main article could discuss it. Alan Mole 00:56, 27 February 2007 (UTC)
Well, the "European driving cycle pattern" is not 90 km/h (56 mph) on Motorways, but 120 km/h (75 mph), which is quite worse on economy-aspects (wind drag is much higher). See also NEDC (or for german speaking people a much more extensive description: VDA.de - Unterschiede der Messmethoden) 129.247.247.238 08:13, 1 June 2006 (UTC)
Which condition does the 140 g/km apply to? 5 L/100 km or 6.5 L/100 km? in fact 5 L/100 km is 115 gm CO2/L, while 6.5 is L/100 km is nearer 150 gm/L CO2. In the UK only one mandatory fuel-consumption figure is used to generate a gm/L figure, which is used in the car tax regime. —Preceding unsigned comment added by 82.45.83.254 ( talk) 18:38, 18 March 2011 (UTC)
The note about European driving cycles yielding higher fuel consumption levels than the U.S. cycle needs correction, and the comparison cited, for the Honda CRZ, appears to be comparing the European test results to the U.S. adjusted (for onroad) values, not the actual test results....the U.S. test results will tend to give LOWER fuel consumption levels than the European cycle in most cases. A 2007 ICCT report on fuel economy standards worldwide gave a 1.12 average adjustment factor (multiply European fuel economy test results by 1.12 to get U.S. test results (in mpg or km/L). However, the report also said that the adjustment factors tended to shrink for higher efficiency vehicles.....today, the Honda CRZ has a U.S. test result of about 5.8/4.5 L/100km (city/highway); versus the cited 6.1/4.4 European results...virtually the same. Steve Plotkin Steveneplotkin ( talk) 17:23, 27 March 2013 (UTC)
When highway speed limits and driving behaviors in the United States regularly exceed 50-55mph, the EPA provided information on highway fuel economy is therefore almost useless. The energy required to overcome aerodynamic drag alone over a given distance is 1.4x greater at 65mph and 1.9x greater at 75mph.
The actual fuel economy achieved on highways may therefore actually be worse than those specifications given for "city" driving.
My expectation is that this article will grow too long for a single article as petroleum becomes scarcer and the US comes to its senses about global warming. So if it is merged in now, it might have to be split off again later. David R. Ingham 03:27, 30 September 2006 (UTC)
Fuel efficient driving redirect to this article , but Fuel efficient driving is also in the See Also of this article, just letting you know --shodan
This needs a lot of work. There are various considerations such as idle consumption. Displacement is really not a primary consideration, it is more weight volume and cost. David R. Ingham 03:36, 30 September 2006 (UTC)
I have wondered about this, but the expert that I consulted on this matter did not think this would happen. Turning the key off while moving and in gear will damage engines and catalytic converters of cars that do not shut off the fuel. David R. Ingham 04:12, 30 September 2006 (UTC)
I added a section on this, and an external link to a more detailed discussion of the legislation. KonaScout 00:04, 11 October 2006 (UTC)
Are SUVs and other cars masquerading as trucks exempted?
It would seem simpler and more straightforward to tax fuel. It is always easy to find some other tax to reduce. David R. Ingham 04:30, 15 October 2006 (UTC)
In Turkey there's a %200 tax on fuel, i.e. if oil is 1 USD/liter without tax, it becomes 3 USD/liter with tax. Also annual taxes for cars are based on engine volume and car age, nothing more. i.e. 2 year old car with 1.6 lt engine is taxed at 400 USD / year whereas a 2 year old car with 4.0+ lt engine is taxed at 10,000 USD/year. These two measures greatly discourage the use of large engines, which corresponds to an overall fuel consumption decrease for the country. —Preceding unsigned comment added by 81.213.159.132 ( talk) 08:35, 21 August 2009 (UTC)
This section needs lots of clean-up! Is it a list of devices consumers can install on a car to achieve greater fuel efficiency, or is it technologies that automakers can employ to provide more efficient cars?
Some of these items are scams or hoaxes (magnets, vaporizers, intake air cyclones), which have their own wikipedia page ( http://en.wikipedia.org/wiki/Aftermarket_fuel_economy_device).
The "Quasiturbine" is a type of engine, like the Wankel Rotary engine or the reciprocating four-stroke engine. That in and of itself is not enough to be considered a fuel-saving technology, as one could easily design a Quasiturbine to have greater fuel consumption than an equally powerful conventional engine.
Torque converters "lock" or "lock up", they don't get "locked out."
"Variable Oxygen Sensor Dial"? This needs to be described. Today's oxygen sensors are variable, in that they return a range of voltages corresponding to the amount of oxygen in a car's exhaust.
"EPROM Fuel Computer Chips for leaner burn"? "Lean-burn" is a combustion strategy that can yield higher fuel economy (usually at a high NOx emissions penalty), but EPROM Fuel Computer Chips is gibberish. "EPROM" is a type of computer memory, "Computer Chips" is a generic way to describe computer components, usually processor-related, and sticking the word "Fuel" in the middle is meaningless.
I'm going to make these changes, but I feel more work will need to be done before this section is good to go.
R.Yo 21:19, 11 November 2006 (UTC)
Also, this section is accompanied by a photo of someone riding in a bus powered by charcoal gas. This has nothing to do with fuel economy; this photo should be deleted or moved to an article on alternative fuels. R.Yo 22:06, 11 November 2006 (UTC)
I just did a partial rewrite of the section covering the EPA test methods, as those have been revised as of December 2006 for use on MY2008 vehicles. Additionally, the CAFE standard does not use (and as far as I know, never has used) the EPA fuel economy ratings - so changes in the EPA methods have zero effect on CAFE. Ayocee 14:09, 2 January 2007 (UTC)
Fatter U.S. drivers guzzle more gas, spend extra $2.8 billion annually. -- 217.72.64.8 06:51, 20 January 2007 (UTC)
The title of this article is very childish. How about Automotive fuel economy? X570 06:30, 30 January 2007 (UTC)
Excuse me, but wtf does "MJ/L" "MJ/kg" "BTU/imp" and "BTU/US" mean?!? Was this written by some acronym geek for other acronym geeks? JayKeaton 15:59, 8 February 2007 (UTC)
"While following large transportation vehicles such as trucks or buses can be tedious, on motorways or highways they assist in reducing drag, pushing through the air and leaving your vehicle a large pocket of turbulence to drive behind." Isn't this highly dangerous considering your probably going to have to tail gate that other vechicle so closely to noticeablly reduce drag there's no way you could stop if they hit their breaks sudenly? Jon 18:08, 30 March 2007 (UTC)
Energy Tax Act says the law was passed in 1979, not 1978. Which article is correct? -- Beland 21:04, 16 May 2007 (UTC)
Nempimania & Hypermiler contain about two-three sentences each about the terms in their title. Everything else in both articles is so general that it overlaps considerably with this article. Both should be merged into here. Hypermiler in particular spends more than 3/4 of its length discussing techniques to increase fuel economy, which are mainly dealt with here in a short bulletted list. This article, too, would benefit from the merge. Any objections? MrZaius talk 16:48, 28 May 2007 (UTC)
Governments and environmental organizations urge drivers to adopt driving patterns that minimize their use of fuel, calling them Ecodrivers in Europe, Hypermilers in America, or urging them to obsess to the point of Nepimania in Japan.
Merge completed to Fuel economy maximizing behaviors to prevent it from dominating this article, given the length of the content found in Ecodriving. MrZaius talk 10:03, 3 June 2007 (UTC)
Why is idling not included in this section?-- John of Paris 08:40, 3 June 2007 (UTC)
The article points out that the speed is highly significant for the mileage. But at what speed is an average mileage measured? 90 km/h? --17:54, 16 July 2007 (UTC)
Right now Fuel economy does not exist, it is simply a redirect to Fuel economy in automobiles, this article. There is a separate article Fuel efficiency, which covers the generic issues of fuel economy. 199.125.109.135 06:35, 18 August 2007 (UTC)
"Headlights, media systems, and other electronics do not increase fuel consumption, as the energy to power these devices comes from the charging system; either the alternator or battery."
This is wrong. Putting a higher electrical load on an alternator causes it to take more mechanical energy from the engine via its drive belt. There's no free energy. 69.205.237.124 20:56, 22 September 2007 (UTC)
I started assembling a chart showing actual and required fuel efficiency in various countries, since this information is somewhat scattered about in prose. But we need more numbers for more countries. -- Beland ( talk) 21:41, 4 February 2008 (UTC)
I was reading some news and stumbled upon this article that might provide some useful information for this article. Quite a few facts are presented in this article that might be useful for citations.
"The Good News and Bad News On U.S. Fuel-Economy Trends"
by Joseph B. White
October 1, 2007
Wall Street Journal
URL:
http://online.wsj.com/article/SB119099903267842827.html?mod=hpp_us_personal_journal
Archive URL:
http://www.webcitation.org/5WLHShMhd
Formatted for inline citation: [1]
-- Smiller933 ( talk) 17:19, 15 March 2008 (UTC)
References
{{
cite web}}
: Check date values in: |date=
and |archivedate=
(
help)
"Social issues - In Sweden statistical analysis has shown that men do buy less energy efficient cars. The average CO2 emissions for men in Sweden is 184.1 g/km and for women 169.2 g/km (-8.1%).[8]"
Although emissions and fuel mileage are often correlated, they are in no way a function of one another. In other words, higher CO2 doesn't necessarily mean that someone is driving a less energy efficient vehicle. —Preceding unsigned comment added by Daveclark35 ( talk • contribs) 15:37, 5 April 2008 (UTC)
In a related matter, does anyone think that fuel economy should be kept out of the automobile infoboxes? Please voice your opinion at http://en.wikipedia.org/wiki/Template_talk:Infobox_Automobile#Vote_on_Fuel_Economy_in_the_Infobox 198.151.13.8 ( talk) 18:28, 7 May 2008 (UTC)
It is this kind of numerical nonsense that is used by lobbyists and politicians to justify irrational policies.
"switching from a 10 mpg vehicle to a 15 mpg vehicle" allows you to travel 5 miles further on that gallon, a 50% increase.
"switching from a 50 mpg vehicle to a 100 mpg vehicle" gets you 50 miles farther, a 100% increase.
So, the savings in the first case is half that of the second, not 3 times!
Only a deeply entrenched auto executive would try to argue that doubling fuel efficiency (vs half again as much) is a diminishment.
69.159.26.193 (
talk) 20:48, 17 June 2008 (UTC)
I can understand people wanting to use the more familiar (to them) km/l designation. But it is absolutely ridiculous to use km/l in the EPA section of the article. The EPA is an American agency which deals in m.p.g. Hell, you'd be hard pressed to find anyone in the US who has any conception of what km/l really means. —Preceding unsigned comment added by 137.28.228.112 ( talk) 18:19, 5 September 2008 (UTC)
Actually I don't understand the usage of Imperial units. Do all the world other than the Americans and Brits (which is 95% btw) have to search for "what is the corresponding SI unit for this gallon, is it US or imperial gallon..." Correct usage should be lt/100km imo. 81.213.159.132 ( talk) 09:18, 21 August 2009 (UTC)
A petrol (gasoline) engine will produce around 2.32 kg of carbon dioxide for each litre of petrol consumed. Can anyone explain to me how this is possible if a litre of petrol does not even weigh 1 kg??? Shouldn't this be 2.32 grams per litre? (my chemistry knowledge is poor, I admit) Lexw ( talk) 20:59, 17 April 2009 (UTC)
The article is correct. The oxygen in the CO2 weighs far more than the carbon. Greglocock ( talk) 02:02, 18 April 2009 (UTC)
This is true. Petroleum is composed of hydrocarbons pentane to octane. Octane has the chemical formula C8H18, which has an atomic mass of (8*12 + 18 =) 114 g/mol (assuming Carbon is 12 and Hydrogen is 1). CO2 has an atomic weight of (12 + 2*16 =) 44 g/mol (assuming Oxygen is 16). Therefore, assuming the combustion of all 8 carbon atoms, 8 molecules of CO2 has a mass of (8*44 =) 352, which is over three times the mass of the original hydrocarbon. The same is true of all hydrocarbons in petrol; pentane (at the other end of the scale) is C5H12, which has an atomic mass of (5*12 + 12 =) 72 g/mol, but the CO2 produced is (5*44 =) 220. Obviously the mass increase is due to the addition of oxygen, despite the oxidation of hydrogen to water, since hydrogen is the least massive atom, whereas oxygen is 16 times its weight and two atoms of oxygen are joined to each atom of carbon in carbon dioxide. Derekjc ( talk) 21:30, 13 June 2010 (UTC)
27 mpg for the US market? Pretty sure there are a lot of cars with worse mileage than that out there… like, most of the cars on this list. Maybe the average of the whole fleet of an automaker? But what about Ferrari or Hummer, they don't have a single car with such a mileage… or are they counted as Fiat and GM, respectively? The 43 mpg number for China sounds even crazier… Basically there needs to be a lot more sources and explanations for this table, otherwise it's pretty useless. – Kloth ( talk) 18:08, 13 August 2009 (UTC)
The data for the UK fuel economy (or more correct CO2) ratings are incorrect. The correct values follow.
Band | CO2 emission (g/km) |
---|---|
A | Up to 100 |
B | 101-110 |
C | 111-120 |
D | 121-130 |
E | 131-140 |
F | 141-150 |
G | 151-165 |
H | 166-175 |
I | 176-185 |
J | 186-200 |
K* | 201-225 |
L | 226-255 |
M | Over 255 |
These bands are used by the DVLA to determine Vehicle Excuse Duty (aka Road Tax) for cars registered after 1 March 2001; found on the Direct Gov website ( http://www.direct.gov.uk/en/Motoring/OwningAVehicle/HowToTaxYourVehicle/DG_10012524). Derekjc ( talk) 21:53, 13 June 2010 (UTC)
"Fuel economy" is a particular quantity defined by "distance/volume". This general article is about, and should be titled, "Automotive fuel usage" with redirects from "fuel consumption in automobiles and " and "fuel economy in automobiles" —Preceding unsigned comment added by 138.194.37.80 ( talk) 03:09, 21 August 2009 (UTC)
The result of the move request was not moved. Fuel consumption in automobiles has already been redirected here. Jafeluv ( talk) 13:06, 15 September 2009 (UTC)
Fuel economy in automobiles → Fuel_usage_in automobiles — The article is about fuel usage, as measured by the reciprocal quantities "fuel economy" (mpg) and "fuel consumption" (L/100 km). There should be a redirect from "Fuel_economy_in_automobiles" and "Fuel_consumption_in_automobiles" Adamtester ( talk) 06:11, 4 September 2009 (UTC)
The article Miles per gallon needs to be merged into this one. That article is mostly
To the extent that the tables are noteworthy (not sure they are) these can be merged into this article or put in a list article. The rest of it can obviously be merged here. There is no evidence that there is enough that is unique about "miles per gallon" that could be stated to merit a separate article. And regardless, certainly that unique content is not there now.
Dissenting opinions?
-- Mcorazao ( talk) 20:52, 23 May 2010 (UTC)
Good idea Greglocock ( talk) 02:20, 24 May 2010 (UTC)
I'm sort of curious of the sticker pic that say "25 MPG average, expect 21 to 29 in real-world driving".
I'm more used to the fact that numbers quoted by European automakers are hopelessly inflated. That is, converted to US MPGs, my car should make 50 MPG highway, 34 MPG city (European manufacturers' data FWIW). In fact it makes a warm season's average of 29, that's all off-peak city driving. The EPA data for the same engine/transmission/grossweight in a different body style are 40 highway, 29 city - spot on.
Is this a regular pattern (that EPA is closer to real life than Euro-specs) or it is just a random sample?
East of Borschov ( talk) 11:41, 10 June 2010 (UTC)
Hi, I'm too mathematecally stupid to derive this on my own. Could anyone give me a formula to convert the percentage of fuel savings into the percentage of the corresponding mileage gain? Like in, if a new model uses x per cent less fuel than the previous model, by how many per cent does the milage increase?-- Cancun771 ( talk) 06:57, 5 November 2010 (UTC)
Here's a quote from the Gallons per mile section as it currently reads (with a minor typo fixed, the reference removed and the {{convert}} call written out explicitely).
For example, replacing a car that gets 14 mpg-US (17 mpg-imp; 17 L/100 km) with a car that gets 25 mpg-US (30 mpg-imp; 9.4 L/100 km) saves 3 US gallons (2.5 imp gal; 11 L) of fuel every 100 miles (160 km). Because 1 US gallon (0.83 imp gal; 3.8 L) of fuel emits 20 pounds (9.1 kg) of carbon dioxide, saving 3 US gallons (11 L) of fuel every 100 miles (160 km) saves 3 short tons (2.7 t) of carbon dioxide every 10,000 miles (16,000 km) of driving.
Let's look at these conversions. I believe that we would generally agree that conversions should provide readers with a clear and accurate picture of what the original text attempts to illustrate. In order to judge whether this example lives up to this let's filter this text.
Let's first apply an imperial filter. Here's what we'll get.
For example, replacing a car that gets 17 mpg-imp with a car that gets 30 mpg-imp saves 2.5 imp gal of fuel every 100 miles. Because 0.83 imp gal of fuel emits 20 pounds of carbon dioxide, saving 2.5 imperial gallons of fuel every 100 miles saves ??? of carbon dioxide every 10,000 miles of driving.
Now, we should note a potential for rounding error here.
So going from US to imperial the difference in miles per gallon was rounded down but the difference in gallons used per 100 miles was also rounded down. Thus the first of these two rounding errors partially cancells the second such that the total error is about 2.9%. So replacing a car that gets 17 mpg-imp with a car that gets 30 mpg-imp actually does save 2.5 imp gal of fuel every 100 miles.
100 mi ÷ 17 mpg-imp = 5+15⁄17 imp gal
100 mi ÷ 30 mpg-imp = 3+1⁄3 imp gal
This gives a difference of 2+28⁄51 imp gal, which is approximately 2.5 imp gal. Thus, all's well so far when we look through our imperial filter.
But now we come across this. "0.83 imp gal of fuel emits 20 pounds of carbon dioxide". Why in the world would we be considering how much CO
2 is emitted when 0.83 imp gal of fuel is burnt? What kind of number is 0.83? This is what I'm calling a "misconversion". The original ratio was "20 lb/US gal" and we converted the wrong part. "20 lb/0.83 imp gal" is pure nonsense imparting very little understanding to our imperial-minded readers. The sensible conversion is, of course, "24 lb/imp gal".
How much does this amount to in tons of CO
2 per 10,000 miles, then? 3 short tons ... short tons ... ? Wait a minute ... 2.7 tonnes ... what happened to the conversion to imperial? If we're going to bother with imperial gallons, we ought to bother with imperial tons i.e. long tons. So we should convert these 3 short tons into long tons ... but wait.
Compare these:
1. "Replacing car 1 with car 2 saves 3 US gal/100 mi. Saving 3 US gal/100 mi saves 3 short tons per 10,000 mi."
2. "Replacing car 1 with car 2 saves 3 US gal/100 mi, this entails a saving of 3 short tons per 10,000 mi."
Number 2 is more concise but there is a more subtle difference. Number 1 says "Saving 3 US gal/100 mi saves 3 short tons per 10,000 mi." whereas number 2 implies "Replacing car 1 with car 2 saves 3 short tons per 10,000 mi."
Saving 3 US gal/100 mi does indeed save 3 short tons per 10,000 miles which is equal to a saving of 2.7 long tons per 10,000 miles. However, remember that the 3 US gal/100 mi figure was an approximation in the first place. How many long tons are we saving by replacing car 1 with car 2? Well, replacing the 14 mpg-US with the 25 mpg-US car actually saved us 3+1⁄7 US gal/100 mi which saves us 3+1⁄7 short tons per 10,000 miles which is actually 2.806 long tons per 10,000 miles (to four sig figs) rather than 2.7. But what about the (slightly different) 17 mpg-imp vs 30 mpg-imp cars? As with the previous calculation, the errors partially cancel leaving no difference when rounded to two significant figures.
Thus it's still accurate to say the following.
For example, replacing a car that gets 17 mpg-imp with a car that gets 30 mpg-imp saves 2.5 imperial gallons of fuel every 100 miles. Because the combustion of 1 imperial gallon of fuel emits 24 pounds of carbon dioxide, this will save 2.7 long tons of carbon dioxide every 10,000 miles of driving.
I think therefore, we could justify the following.
For example, replacing a car that gets 14 mpg-US (17 mpg-imp) with a car that gets 25 mpg-US (30 mpg-imp) saves 3 US gallons (2.5 imp gal) of fuel every 100 miles. Because the combustion of 1 US gallon of fuel emits 20 pounds of carbon dioxide (1 imp gal emits 24 lb), this saves 3 short tons (2.7 long tons) of carbon dioxide every 10,000 miles of driving.
But now let's apply our metric filter. This is where the fun really begins.
For example, replacing a car that uses 17 L/100 km with a car that uses 9.4 L/100 km saves 11 L of fuel every 160 km. Because 3.8 L of fuel emits 9.1 kg of carbon dioxide, saving 11 L of fuel every 160 km saves 2.7 t of carbon dioxide every 16,000 km of driving.
Not really, replacing a car that uses 17 L/100 km with a car that uses 9.4 L/100 km saves 7.6 L/100 km which is 12.16 L/160 km not 11 L/160 km. So, it's not accurate at all, there an approximate 11% error here. But wait ... why ... oh, why are we talking litres per 160 km? What's the significance of this number 160? None. In the metric world, none at all. Here again is what I'm calling misconversion. A conversion from US gallons per hundred miles to litres per hundred miles is as useful as windscreen wipers on a submarine. This is not a conversion to metric, it's a conversion to mongrel. Further, what kind of example is this? Replacing a car that uses 17 L/100 km with a car that uses 9.4 L/100 km? Why choose such a number as 9.4 for an example? Why not a nice round number like 9 or 10?
Next, "3.8 L of fuel emits 9.1 kg of carbon dioxide" ... how many litres? Is there anything special about 3.8? Here's another misconversion. 20 pounds per US gallon is 2.4 kilograms per litre. "9.1 kilograms per 3.8 litres" is rubbish. More rubbish follows with 2.7 tonnes per 16,000 kilometres. What's the sense in a conversion to tonnes per 16,000 km? We want tonnes per 10,000 km.
How can we rescue this example? We might like to round 9.4 down to 9. The we're saving 8 L/100 km. This saves us 1.917 t of CO
2 per 10,000 kilometres. But 3 short tons per 10,000 miles is 1.691 t/10,000 km. Rounding up to 10 would give 1.678 t/10,000 km so we could accurately say "3 short tons per 10,000 miles (1.7 t/10,000 km)" but "25 mpg-US (10 L/100 km)" would not be valid. Perhaps the best thing would be to split the example up like this.
For example, replacing a car that gets 14 mpg-US (17 mpg-imp) with a car that gets 25 mpg-US (30 mpg-imp) saves 3 US gallons (2.5 imp gal) of fuel every 100 miles. Because 1 US gallon of fuel emits 20 pounds of carbon dioxide (1 imp gal emits 24 lb and 1 L emits 2.4 kg), this saves 3 short tons (2.7 long tons) of carbon dioxide every 10,000 miles of driving. Similarly, replacing a car that uses 17 L/100 km with a car that uses 10 L/100 km saves 7 L of fuel every 100 km. This represents a saving of 1.7 t of carbon dioxide every 10,000 km of driving.
But was there anything special about 14 mpg-US and 25 mpg-US in the first place? What about choosing different numbers? How about 16 mpg-US and 30 mpg-US? 16 mpg-US is about 19.215 mpg-imp or 14.701 L/100 km. 30 mpg-US is about 36.028 mpg-imp or 7.840 L/100 km. Now for a little rounding off and we're replacing a car that gets 16 mpg-US (19 mpg-imp or 15 L/100 km) with a car that gets 30 mpg-US (36 mpg-imp or 8 L/100 km).
So 16 mpg-US → 30 mpg-US still saves about 3 US gal per 100 mi, 19 mpg-imp → 36 mpg-imp still saves about 2.5 im gal per 100 mi and we've now got a nice round 7 L/100 km. So we could reword the whole thing like this.
For example, replacing a car that gets 16 mpg-US (19 mpg-imp or 15 L/100 km) with a car that gets 30 mpg-US (36 mpg-imp or 8 L/100 km) saves 3 US gallons (2.5 imp gal) of fuel every 100 miles (7 L/100 km). Because the combustion of 1 US gallon of fuel emits 20 pounds of carbon dioxide (burning 1 imp gal emits 24 lb and burning 1 L emits 2.4 kg), this saves 3 short tons (2.7 long tons) of carbon dioxide every 10,000 miles (1.7 t every 10,000 km) of driving.
JIMp talk· cont 08:22, 7 August 2011 (UTC)
It seems to me the entire "Units of measure" section is needlessly complicated and laden with so much alphabet soup that it does more to confuse the issue than explain it.
This may spring from my ignorance of the field, but, describing fuel consumption and fuel economy as two different things ("fuel per distance" and "input per output") seems absurd. Both measure exactly the same thing - the relationship of fuel consumed to distance traveled. It's just a question of which unit is in the numerator. Why not state this as "fuel per unit distance" and "distance per unit fuel"? This would make the inverse proportionality more intuitively clear to the reader.
Likewise, much of this section is bogged down in unit conversions - would it work better if the table at the end of the "Gallons per mile" section was higher up, and the discussion of the math stuck to a single unit?
Finally, the "Inverse or reciprocal scale" section seems to make the argument that one measurement is better than the other for comparing the fuel efficiency of automobiles. Again, they both measure the same thing, and the mathematical operation to compare them (dividing one by the other) will give the same result.
10 MPG = 0.1 GPM
20 MPG = 0.05 GPM
20 MPG / 10 MPG = 2, an improvement by a factor of 2.
0.1 GPM / 0.05 GPM = 2, an improvement by a factor of 2.
You have to flip the division order, because you've flipped the units; however, even if you don't, you're going to get the proportionality constant (or its reciprocal) out. It's the same number because by finding the factor of improvement, you cancel out the units. The consumer confusion mentioned in this section seems not to be due to the inverse relationship (as it claims), but because consumers are comparing the numbers by looking at the difference in values, rather than the factor between them.
I didn't want to make any changes (I know a lot more about manipulating units than I do about cars), but hopefully this will draw more informed editors' attention to the confusing nature of the section. I came across this page today, and spent a good 10-15 minutes trying to decipher what it was trying to convey, and I teach general chemistry - I fiddle with these types of unit conversions every day. I can't imagine how confusing it would be to the average consumer.
Of course, if my thinking is way off base here (entirely a possibility) please feel free to correct me. Thanks! StellarFury ( talk) 00:02, 10 December 2011 (UTC)
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The article correctly says that L/100km is the measure of fuel economy used in Australia, New Zealand and South Africa. However, the diagram says "MPG to l/100km conversion chart: blue: US gal, red: imp gal (UK and British commonwealth)"
This is wrong in several ways:
To remedy this inaccuracy, I suggest the following change:
I also suggest spelling out the words for greater ease of reading. Michael Glass ( talk) 13:50, 10 February 2013 (UTC)
Diagram label changed as proposed. Michael Glass ( talk) 21:51, 11 February 2013 (UTC)
I have noticed that the article frequently uses a lower case l as a symbol for litre. The BIPM allows both the lower case l and the upper case, but it notes that the lower case l is liable to be confused with the numeral 1 See the BIPM brochure (PDF), page 38. I therefore propose that the the upper case L be used consistently throughout the article.
Are there any comments or concerns? Michael Glass ( talk) 21:48, 11 February 2013 (UTC)
I have moved HCCI from the section Engine combustion strategies to the section Future technologies. No-one is in production with HCCI as of Jan 2014, and I'm not sure it will happen as soon as proposed by some OEMs either. Mike163 ( talk) 17:02, 17 January 2014 (UTC)
Following text (taken from the old Low-energy vehicle page) can be added to the fuel efficiency statistics page;
Higher efficiency can be achieved by changing the vehicle's design, and/or by modifying its powertrain. Energy consumption as low as 5-12.5 kWh/100 km (180-450 kJ/km) is achieved directly by battery electric microcars. When comparing the efficiency of electric cars with IC cars the efficiency of the power generation has to be considered, for example the distribution efficiency for Europe is about 40%, [1] so the overall energy consumption of electric cars lies in the range 0.45 to 1.1 MJ/km. (Average energy efficiency of US plants 33% US DOE (ref to follow) US grid transmission loss 9.5%, UK grid transmission loss 7.4 (ref Wikipedia national grid entry) - transmission losses not included in electric car efficiency figure.) By the year 2050, consumption levels of 1.6 l/100 km (0.64 MJ/km) in diesel-fuelled cars and 2 l/100 km (0.7 MJ/km) in petrol-fuelled cars are deemed feasible. [2] The energy consumption figures for petrol and diesel cars also need to be increased by 18% [3] to represent the oil used in processing and distributing oil-based fuel, to 0.75 MJ/km for diesel, and 0.82 MJ/km for petrol.
To put these consumption figures into perspective a consumption of 1000 km/litre (2350 mpg US) is 0.0344 MJ/km, excluding distribution energy. At 20 km/h it would take 50 hours to travel 1000 km, so with a 20% efficient internal combustion engine it would need to attain and keep this speed using just 38.2 watts.
Even one of the most fuel efficient two seater on the market - the Smart MHD- consumes two or three times more energy per km than a cabin based ultralight two seater would - proven by the 1l prototype by VW. Pilot vehicles have proven that a feasible target may lie in the range of 1-2 l/100 km, or lower, or 10 kWh/100 km electricity. Available electric LEVs already use substantially less energy than available cars, e.g. 4–8 kW·h/100 km for the Twike,. [4] Here the challenges are increasing range and lifetime of batteries, crash worthiness, passenger comfort, performance and reducing the price (which is currently about twice that of a cheap conventional four seater).
Energy Efficiency in MJ per km or kWh per 100 km: It is more straightforward to express energy efficiency in MJ (Mega-Joule) per km because terms like MPG (Miles Per Gallon) and litres per 100 km do not take into account what type of fuel is used and thus the numbers will be distorted for different fuel types. Diesel contains 38.7MJ per litre, Gasoline 34.6MJ per litre and Bio-Diesel 30.5MJ per litre, whereas LPG contains only 22.2MJ per liter which is why the number of litres consumed go up drastically when converting a gasoline car to LPG. This does not mean that the energy consumption goes up; it only means that there is less energy in a litre of LPG. Ethanol also contains much less energy per litre than gasoline. To compare electricity and gasoline its easier to use kWh/100 km since 1l gasoline holds around 10kWh.
Energy demand may be kept low by:
Technological support for low energy operation may also come from driver assistance systems since driving style can be adapted to achieve lower energy consumption. Energy management becomes possible with hybrid vehicles with the possibility to recuperate braking energy and to operate the internal combustion engine (ICE) at higher efficiency on average. Hybrid power trains may also reduce the ICE-engine size thus increasing the average load factor and minimising the part load losses. Purely electric vehicles use up to 10 x less energy (0,3 to 0,5MJ/km) than those with combustion engines (3 to 5MJ/km and up to 10MJ/km for SUVs) because of the much higher motor and battery efficiencies.
Average data for vehicle types sold in the U.S.A. [7]:
Type | Width | Height | Curb weight | Combined fuel economy | Percent | Occupancy rate 2005 Florida [8] |
---|---|---|---|---|---|---|
SUVs | 73.5 in 187 cm | 70.7 in 180 cm | 4242 lb 1924 kg | 19.19 mpg 12.25 l/100 km | 328% | |
Minivans | 75.9 in 193 cm | 70.2 in 178 cm | 4275 lb 1939 kg | 20.36 mpg 11.55 l/100 km | 309% | 1.67 |
Family sedans | 70.3 in 179 cm | 57.3 in 146 cm | 3144 lb 1426 kg | 26.94 mpg 8.73 l/100 km | 234% | 1.35 |
Toyota Prius | 66.7 in 169 cm | 57.6 in 146 cm | 2765 lb 1254 kg | 56 mpg 4.2 l/100 km | 112% | n.a |
GM Volt | 70.8 in 180 cm | 56.3 in 143 cm | 3790 lb 1720 kg | 60 mpg 4.0 l/100 km | 105% | n.a. |
Honda Insight [9] | 66.7 in 169 cm | 53.3 in 135 cm | 1850 lb 839 kg | 63 mpg 3.73 l/100 km | 100% | n.a. |
Audi A2 | 65.9 in 167 cm | 61.1 in 155 cm | 1973 lb 895 kg | 71 mpg 3.0 l/100 km | 81% | n.a. |
The drag resistance for an SUV, compared with a family sedan with the same drag coefficient, is approximately 30% higher, and its increased mass means that the acceleration forces has to be 35% bigger for a given acceleration. This gives a 40% increase in fuel consumption. The last column in the table demonstrates that with the exception of the Prius and the pick-ups all the alternatives have roughly the same potential fuel usage per passenger IF they were fully occupied. However the fuel usage per passenger really depends on the occupancy rate of each type. In 2000 the occupancy rate was only 1.6 in practice, decreasing each year, averaged across all vehicle types and journey types, [10] and 1.2 for commuting.
The fuel consumption of an engine is depicted as a 3dimensional map where the consumption is shown against RPM and torque. Normally the smallest consumption is seen in the upper middle part of the diagram. For diesel engines this region is bigger to lower torque and extends to higher RPM. The choice of engine power for a given vehicle should consider the typical application - for non transient low velocity operation this leads to lower power requirements, at the cost of reduced acceleration and top speed. A hybrid electric concept allows an even lower power internal combustion engine, but the added weight pays only off if operating in stop and go conditions frequently or generally at low power, if using a series hybrid electric concept.
The EU- sponsored RECODRIVE project [11] has set up a quality circle to manage low energy consumption in fleets. This starts with energy aware procurement, and includes fuel management, driver information and training and incentives for all staff involved in the fleet management and maintenance process. Vehicle equipped with gear shift indicators, tire pressure monitoring systems and downsized internal combustion engines and for stop'n go operation also hybrid electric power trains will help to save fuel.
KVDP ( talk) 12:20, 11 February 2014 (UTC)
References
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I'd like to propose some changes to this article, mostly regarding restructuring for better readability and flow:
I've got a version of my proposed edits in my sandbox here, and given my COI, I'm happy to collaborate and discuss any concerns or the merits of these suggestions and make changes accordingly before submitting an edit request. FacultiesIntact ( talk) 23:30, 23 March 2015 (UTC)
THS was based on a vehicle built at TRW by Dr. Baruch Berman, Dr. George H. Gelb and Dr. Neal A. Richardson in 1971 so Toyota is NOT the inventor of series/parallel hybrids. Greglocock ( talk) 12:37, 18 July 2015 (UTC)
Hi. FYI the "experimental car" from 1916 pictured is a production car, see this article
Rolling Phantom ( talk) 21:00, 23 June 2016 (UTC)