Talk:Fuel economy in automobiles

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[edit] Graph of mpg versus l/100 km is wrong

the conversion between mpg and l/100km is wrong. It should be linear. This graph should be deleted.

The graph looks fine to me. y(x)=235/x is not a linear function.
It's not y=235/x, the relationship is 1 mile per gallon = 235.2 l/100km. That's a linear relationship. You either multiply or divide by 235.2 depending on which way you're going. It's a straight line on a graph.
Think about that for a second. So if 1 mpg = 235.2 l/100km, then 2 mpg = 470.4 l/100km? 2 mpg is clearly going twice as far per one gallon of gas, but somehow when converting it to l/100km you're saying it converts to using twice the amount of fuel for the same distance traveled? Quite simply, mpg is a measure of "distance per quantity", while l/100km is "quantity consumed per distance". They're inverse units and will not have a linear relationship. Ayocee (talk) 17:12, 17 November 2007 (UTC)
I'm sorry. You guys are right. I using the google calculator and the results are quite nonlinear. Interestingly, if you type "mpg in l/100 km" into google you get a result that seems to imply the misconception of linearity I had.

[edit] Drag

In Drag, is the scaling in consumption per time or consumption per kilometer? Any figure for scaling of consumption per kilometer with speed?

The way of expressing fuel consumption in metric countries is to use litres per 100 km. I would write this as L/(100 km) but I have seen L/100 km and L/100km. L/100 km is wrong according to the precedence rules of algebra and L/100km is wrong because it leaves out the space, which is mandatory (see ISO 1000 or ISO 31). In addtion, use of 100 km is poor use of the metric system, which is specifically designed to avoid the need for arbitary constants. A better solution, in my view is to express fuel consumption in centilitres per kilometre (cL/km). This is numerically equal to litres per 100 km, but can be written tidily. The problem can be seen in the paragraph about motorcycles, where the litres per 100 km figures are in brackets, which makes them look even more clumsy.Blaise 09:18, 14 March 2006 (UTC)

[edit] Relation among energy spent in manufacturing and in operation

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).

[edit] Energy Content

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 have redone the values in this table using data from the Bosch Automotive Handbook, 4th edition. The MJ/kg figures are straight from the reference. Petrol, LPG and diesel densities are typical values only, so MJ/L values can vary with density value used and this obviously affects derived numbers. The octane ratings of fuels other than petrol (gasoline) are not taken from this reference. --Athol Mullen 04:57, 25 November 2006 (UTC)
I would have liked to have put the ref to the right of the table, at the bottom corner. The closest I can seem to get is underneath. If anyone knows how to fix this, please do. --Athol Mullen 05:02, 26 November 2006 (UTC)

[edit] Introduction example

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.

[edit] "accelerate as gradually as possible"

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

"Gradual accelaration is not the same as slow accelaration" Do you mean moving the throttle gently?
Mixture vs. pumping losses: At least since mid century car engine fuel systems have increased the mixture at full throttle, so maximum efficiency is typically around 3/4 throttle. (With low octane fuel, detonation or retarded timing also contributes.) Only with variable valve timing can a spark ignition engine be efficient at less than half throttle, and probably still not as efficient as at more throttle. This is the difference between adiabatic expansion and free expansion. Free expansion is fundamentally wasteful. This is usually referred to as "pumping losses". Now that they are using neural networks to control the mixture, which loop you are in is not a large factor. David R. Ingham 04:33, 30 September 2006 (UTC)

[edit] Difference for automatic vs manual transmission?

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)

[edit] Economical driving: Slow acceleration, low engine speeds?

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)

[edit] Mexican overdrive

"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 disagree. What is the source for this "testing"? Modern, computer-controlled engines base the amount of fuel fed to the engine on the load requested, either from the driver or the computer. An idling engine still needs enough fuel to keep itself running and to drive the accessories (alternator, water pump, power steering pump, etc). When the transmission is in gear and the vehicle is decelerating, the transmission can backdrive the engine, reducing (but not eliminating) the amount of fuel required to keep the engine running. R.Yo 21:19, 11 November 2006 (UTC)
'An example familiar to many fuel economy enthusiasts is the "fuel cut" feature. It's common for fuel-injected engines to stop injecting fuel when the accelerator is released above a certain engine RPM. The problem is that manufacturers don't follow a standard method of describing when this mode is active. The result is that some cars continue to report active fuel injection to the ScanGauge, even when it's not actually happening.' http://www.metrompg.com/posts/scangauge-interview.htm ~kps 64.235.97.125 (talk) 16:28, 2 March 2007 (UTC).

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)

[edit] Measurement cycles

Government-mandated fuel efficiency measurements generally have two regimens or driving cycle patterns: a city or urban cycle, and an highway or extra-urban cycle. In Europe, the two standard measuring cycles for "L/100 km" value are motorway travel at 90 km/h and rush hour city traffic. A reasonably modern European supermini may manage motorway travel at 5 L/100 km (47 mpg US) or 6.5 L/100 km in city traffic (36 mpg US), with carbon dioxide emissions of around 140 g/km.

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)

[edit] US Consumer Information on Highway Fuel Economy is Misleading

This effect is largely due to aerodynamic drag. In highway driving over 80-90 km/h (50-55 mph) the aerodynamic drag will rise sharply, thus increasing fuel consumption.

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.

Although your assessment of EPA mileage ratings is correct (the stated MPG a car gets is rarely accurate), I have yet to drive a car that got worse gas mileage on a highway than in a city. - Runch 18:13, 14 August 2006 (UTC)
The only one I know of that actually gets better gas mile in the city compared to the highway is the Toyota Prius; and that's only if you exclude the first few minutes or so of driving while it warms up the emissions equipment. Jon 18:03, 30 March 2007 (UTC)
It depends upon how one actually drives in both places. Skyemoor 02:17, 25 August 2006 (UTC)
It depends on the characteristics of the engine. Typical engines in developed countries are big and tuned for power, so they are not efficient at low speeds. I saw data somewhere that a typical car got best economey around 60 or 70 mph. David R. Ingham 04:05, 30 September 2006 (UTC)
from article: ...as people in developed countries tend to buy bigger and heavier cars. Then why don't US tend to build and use more fuel efficient vehicles? --217.72.64.8 07:21, 20 January 2007 (UTC)
I saw data somewhere that a typical car got best economey around 60 or 70 mph. Please provide a reliable source for this claim. Skyemoor 18:59, 22 January 2007 (UTC)
I don't know if you count me as reliable, but MY car gets its best fuel economy at exactly 70mph, as tested (extensively) by me. I do know this isn't any good as a source for Wikipedia, however... Midlandstoday 22:14, 18 October 2007 (UTC)
The EPA's fuel economy pages says it's currently 60 MPH and then it starts to make a 5% drop every 5 MPH thereafter. Personally, I found on a 2003 Ford Taurus I didn't notice a significant fuel consumption difference until past 65 MPH. Now on a 2005 Toyota Prius, the difference between 60 MPH and 65 MPH is apprent; and (less so) between 55 MPH and 60, but this is in large part because the Prius tells you exactly what MPH your getting at every instant. Jon 18:03, 30 March 2007 (UTC)

[edit] Merg of Fuel efficient driving into this article.

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

I just removed the link in the See Also section --JVersteeg 17:30, 21 November 2006 (UTC)

[edit] The type of engine paragraph

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)

[edit] "Under certain circumstances, minor long-term engine damage may be sustained."

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)

[edit] Gas Guzzler Tax

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)


[edit] Fuel economy-boosting technologies

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)

[edit] New EPA methods / CAFE

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)

[edit] Fatter U.S. drivers guzzle more gas, spend extra $2.8 billion annually

Fatter U.S. drivers guzzle more gas, spend extra $2.8 billion annually. --217.72.64.8 06:51, 20 January 2007 (UTC)

[edit] Title

The title of this article is very childish. How about Automotive fuel economy? X570 06:30, 30 January 2007 (UTC)

[edit] poorly written

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)

Megajoules per liter, megajoules per kilogram - both measures of energy density though I am not sure which would be preferred / more appropriate. The BTU/imp and BTU/US are incomplete, as the full headings should be read as BTUs per Imperial gallon, and BTUs per US Gallon, as the two are different measures of volume. Curious that you would use 'wtf' in a post complaining about acronyms. Ayocee 18:01, 19 February 2007 (UTC)

[edit] excuse to tail gate?

"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)

Following at an unsafe distance would indeed incur risks. However, large trucks have a deep 'shadow' of turbulence, and can provide some drag reduction benefits even at a safe distance. --Skyemoor 14:25, 3 May 2007 (UTC)
Not likely. A safe distance is defined as three seconds, which is way outside of drafting distance. 199.125.109.31 22:33, 13 July 2007 (UTC)
Defined by who as 3 seconds? Round here (UK) the recommended distance is 2 seconds, with a sometimes-quoted minimum of 0.5 sec. Midlandstoday (talk) 20:44, 26 November 2007 (UTC)

[edit] Energy Tax Act accuracy question

Energy Tax Act says the law was passed in 1979, not 1978. Which article is correct? -- Beland 21:04, 16 May 2007 (UTC)

That article says it was enacted in 79, not that it passed in 78. There's a decent chance that both are correct, although it certainly warrants verification. MrZaiustalk 16:48, 28 May 2007 (UTC)

[edit] Merger discussion

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? MrZaiustalk 16:48, 28 May 2007 (UTC)

Well I for one object. I think Fuel Economy is a design, Hypermiling is a behavior. I definately agree that the articles should be linked to fuel economy, but feel that they should be seperated from the fuel economy page since they are behavioral. I feel this applies to Ecodriving, Nempimania & Hypermiler. DKBryanttalk 12:50, 01 June 2007 (UTC)
Does it? Fuel_economy_in_automobiles#Fuel_economy-boosting_actions_and_technologies exists, and seems to be covering exactly the same ground. There's so little difference between the three terms you linked, and so much overlap between their articles and the section I just mentioned that they could easily be merged into a single section here with an opening sentence reading:

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.

Also keep in mind that all three are such rarely used neologisms that, stripped of the content that plainly belongs here, they'd be left with only a sentence or two each in their leads, defining the three concepts in almost identical terms. MrZaiustalk 12:33, 1 June 2007 (UTC)
I've got to agree with MrZaius here, those are methods / behaviors that are a subset of the fuel economy idea. Ayocee 15:12, 1 June 2007 (UTC)
Still disagree, although probably on more personal reasons than impartial ones. Taking the Ecodriving and Nempimania articles out of the equation, as those are really stub articles, I see little more than bullets on behavior in the fuel economy entry. There are no mentions of Pulse & Glide which is far and away the most efficient use of commonly tuned internal combustion engines. Behavior is the single largest component of fuel efficiency, much more so than engine design or even displacement. The term "fuel economy" in no way eludes to a behavior, but rather an empirically tested value. I see it in the same vain as merging Conservation movement into Greenhouse gas, conservation reduces greenhouse gases, just as Hypermiling increases Fuel Efficiency. Still only one vote, but I vote against merging.DKBryanttalk 22:28, 01 June 2007 (UTC)
Support : Neipmanica is all of one paragraph. Hypermiling appears to be a subset of this article. Jon 17:44, 1 June 2007 (UTC)

Merge completed to Fuel economy maximizing behaviors to prevent it from dominating this article, given the length of the content found in Ecodriving. MrZaiustalk 10:03, 3 June 2007 (UTC)

[edit] Factors in fuel economy

Why is idling not included in this section?--John of Paris 08:40, 3 June 2007 (UTC)

It should be. In Germany the law requires shutting off the engine at railroad crossings. 199.125.109.31 22:35, 13 July 2007 (UTC)

[edit] Km/h at what speed

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)

The short answer is over the total distance travelled. The long answer is that fuel economy is measured on a dynamometer over a specified driving cycle. The cycle used is different in the US than it is in the EU. See article for references. 199.125.109.31 02:54, 30 July 2007 (UTC)

[edit] Rename article to Fuel economy

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)

[edit] charging system

"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)

Agreed. I updated the text accordingly - although it should definitely be noted that the effect from the electrical system is rarely more than minimal, and is one of the smallest factors in determining the fuel economy of a given driver / vehicle. A worst-case scenario for most cars would be a total draw of 60-80A; at 12V that's 720-960W. Figuring for an alternator's efficiency and the sake of easier to work with numbers, if we peg the alternator's additional load at 1000W over its 'normal' running condition, that's a drag of a bit over 1.3 horsepower. Considering that not many people would be loading their electrical systems to that extent on a constant basis, the fuel economy hit presented by it would be minimal compared to that of air conditioning, underinflated tires, or a heavy right foot. Still very much present, though. Ayocee 17:10, 24 September 2007 (UTC)

[edit] More statistics needed

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)

That's a great idea. Are you using US gallons or imperial (etc)??? Perhaps a chart would be better, although I suppose it would be more work to create it and keep it live. And it might even count as OR. I'll look out figures for Oz. Remember to give references.Greg Locock (talk) 23:06, 4 February 2008 (UTC)

[edit] Possible source for this article

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)


[edit] Social Issues Section is Incorrect

"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)

Try plotting claimed fuel economy vs CO2 emissions for petrol or diesel engines. There is a very good reason why they are almost 100% correlated. On what do you base your argument? Greg Locock (talk) 01:55, 6 April 2008 (UTC)
The consequent may be true, but it does not follow from the antecedent: if men and women bought exactly the same kind of car, but women drove them faster, we would expect women to use more fuel, and hence emit more CO2. mdf (talk) 16:47, 28 April 2008 (UTC)
"Although emissions and fuel mileage are often correlated, they are in no way a function of one another." is just plain wrong. Greg Locock (talk) 01:05, 29 April 2008 (UTC)
No it's not. "In other words, higher CO2 doesn't necessarily mean that someone is driving a less energy efficient vehicle." If you buy a massive, piggy SUV with the fuel economy of a battle tank ... but leave it parked in your driveway, except on nights of a full moon, your emissions are going to be smaller than a Prius that is driven 100km every day. If, as you aver, emissions are functions of fuel mileage, how do you explain this result? If you have to introduce another variable into the discussion to do so, then the article proper should receive the same treatment.
Which is the core of Daveclark35's argument. mdf (talk) 12:25, 29 April 2008 (UTC)
OK, I forgot we are arguing in greeny world. You win, by your logic. Meanwhile, I suggest you look up figures for CO2 emissions in g/km, and fuel consumption, in say litres/100km, and plot them against each other. Greg Locock (talk) 12:57, 29 April 2008 (UTC)
"If you buy a massive, piggy SUV with the fuel economy of a battle tank ... but leave it parked in your driveway" This doesn't change the fact that the line quoted in the opening post of this topic specifies CO2 emissions in g/km - the average is based on grams per kilometer driven, not grams released total. Yes, a Prius that is never parked will have higher total carbon emissions than a Suburban that gets driven once a month - but per kilometer driven, there's no comparison. Ayocee (talk) 14:00, 29 April 2008 (UTC)
Once again, this is not true in general. Suppose both parties purchase a Prius and drive it exactly the same distance every day. However, the woman has a type-A personality and drives it faster than the man. Who has the higher emissions? mdf (talk) 14:53, 29 April 2008 (UTC)
Your logic is flawed here. The spreadsheet used as the source is based on data from car manufacturers - this is g/km driven that is determined on a standardized test that eliminates driving style as a variable. According to that study, it shows that men in Sweden on average buy cars that, according to that test, release more CO2.
All that said, I don't think that section needs to be in the article - it's a one-line stub that doesn't seem to add anything of any real value to the article. Ayocee (talk) 16:16, 29 April 2008 (UTC)
Flawed? The logic appears to be fine. Maybe irrelevant is the word you wanted to use? If so, I'll note what the article says: "The average CO2 emissions for men in Sweden is 184.1 g/km and for women 169.2 g/km (-8.1%)." If it was corrected to read "The CO2 emissions, per distance driven while under standard test conditions, for cars that men buy in Sweden [...]" (or a better written equivalent), the issue is indeed resolved to a large extent.
But even that version of the statement has a tinge of "those filthy, piggish, Swedish men are laying waste to the planet!" to it. This is why that though the fact may be true, I don't think we can not completely divorce ourselves from end-use to which the vehicle is put. Maybe it is indeed better to just remove the statement, until someone publishes a more formal analysis on the subject. Mind you, the source itself should somehow remain. mdf (talk) 17:19, 29 April 2008 (UTC)

[edit] Fuel Economy infobox

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)