Fuel Consumption

[evoWalo]

This isn't really a topic that JW's known for and few would care but recently I've been keeping track & comparing my actual fuel consumption vs manufacturer's published MPG/KPL. The difference is a bit concerning. For example a '01 C-Class 200 Kompressor 'matic sedan is said to do 32.1MPG/13.7KPL but my experience has mine pegged at 15.3-17.6MPG/6.5-7.5KPL. This makes it pretty much half of what it should do. It's almost as bad as the Evo!

Would humidity & temperature have an influence?

[astonmartinandy]

To be honest it's best not to get to concerned about fuel consumption or it will become more important to you than driving itself! 8)

Yes, fuel costs a ridiculous amount of money and consumption is not a major issue in my little car, but you still have to enjoy every last gallon as much as possible.. or buy a 1 cylinder diesel engined Smart car

[sentra_dude]

I keep track of my mpg, and I manage better mpg on both the highway and in the city than the EPA's estimate, even when I am not easy with the throttle.

city/highway
EPA: 22/29mpg

Me: 24-25/32-34mpg

I don't think I have ever managed to get 22mpg...I guess those EPA testers floor it a lot.

Now that gas prices are starting to get a little high in the U.S. (everyone here is complaining about it, despite the fact the prices are still lower than most if not all of Europe) it makes me glad I have a reasonably fuel efficient car.

[TransAm]

My SAAB computer says I am getting 26.2 MP(UK)G* Not bad for a tuned automatic that gets driven in the city most days IMO. This is the average over the last 1000miles or so (since i last reset the trip computer). The saab computer is supposed to be a little optimistic, but its not that far out.

Before I upgraded the software on the car I was getting about 28MPG.

*MP(UK)G = UK Gallons, UK gallons are 20% bigger than US gallons. Yes I know I buy petrol from the 'gas' station in US gals but UK gallon MPG means more to me.

If I press reset on the display at 55-60MPH I get about 43 MPG., IIRC, but that will only stay constant if you don't accelerate or hit a hill!

[oscargarza88]

the dodge ram i drive once in a while does abour 15 miles to the gallon, this is driving slow, with no hurry at all. stepping on it i have seen 9 miles to te gallon no, i think i ve seen 8.
this is due to a biig thirsty 5.7 V8 HEMI

[TransAm]

^ when I first moved to the US I was going to buy a Ford 150 Lightning. Fuel consumption on a long test drive (I topped off the tank) put me right off. 10MPG!

[nthfinity]

transam, i used to own a Saab 9000 turbo w/5 speed a while ago, and experienced the same thing....

with a 17.9 gal tank, i never once filled more then 15.8 gallons in it (i usually stayed in the red on the gas guage for a few weeks) my average consumption was about 550-600 miles per tank (34.8-38mpg) and hit similar constant velocity instantaneous mileage at 65 mph (2800 revs about)

i now average about 14 mpg in my Jeep... but i get about 21-22mpg highway, which is right on with the sticker

EPA figures do not come from everyday road driving but rather from tests done in an air conditioned lab. They run several routines to simulate stop-n-go traffic and highway driving. The tests are then adjusted anywhere from 10 - 25% to more accurately approximate the real world. This does not accomodate adequately for changes in elevation or weather or tires being out of balance/incorrect pressure etc. The EPA further does not account for the fact that a performance car will not be driven like an econobox or that trucks will be at times towing/hauling and are very aerodynamically inefficient

[Sir_GT]

I've read somewhere that the manufacturer's published data are based on tests carried out on a machine similar to a dyno... which is apparently why it doesn't necessarily equate to the actual figures.

Whether or not that's true, I have no idea.

[evoWalo]

Originally Posted by TransAm2001 My SAAB computer says I am getting 26.2 MP(UK)G* Not bad for a tuned automatic that gets driven in the city most days IMO. This is the average over the last 1000miles or so (since i last reset the trip computer). The saab computer is supposed to be a little optimistic, but its not that far out. Before I upgraded the software on the car I was getting about 28MPG. *MP(UK)G = UK Gallons, UK gallons are 20% bigger than US gallons. Yes I know I buy petrol from the 'gas' station in US gals but UK gallon MPG means more to me. If I press reset on the display at 55-60MPH I get about 43 MPG., IIRC, but that will only stay constant if you don't accelerate or hit a hill!

Dude thanks for pointing out the diff of UK & US gallons! I got the manufacturer fuel consumption for a UK site. A UK mile is still a US mile?


Manufacturer's stated is now 32.1MP(UK)G/11.4KPL

[DeMoN]

What Manufacturers say is what you could do if you drive only highway and dont ever go over 2k revs. That would be the only way to get very close to the suggested MPG consumption. On the other hand, if you live in the city and do several stops and drive like I do....



This is what I get. (According to Infiniti, I should do 38 I think but Im doing 9 to 13)

I hate driving like an old lady so I must pay a lot =/

BTW this is US Galons and yes 1 mile is 1 mile anywhere.

[Wutputt]

Originally Posted by Sir_GT I've read somewhere that the manufacturer's published data are based on tests carried out on a machine similar to a dyno... which is apparently why it doesn't necessarily equate to the actual figures.

Like nthfinity said, they are done on a dyno in a labo. Those test are mandatory and imposed by the government. They are introduced to retrieve the emissions of a certain vehicle and its fuel consumption. Via this way the government can find out if a vehicle complies with the current emission standards.

I don't really know the US situation, but in Europe manufacturers have to publicise those figures in their brochures. They may not publicise other figures. The problem with those tests is the fact they aren't really accurate. The reason is those test don't ask really hard accelerations like in real life. I've uploaded a combined ECE/MVEG test cycle. It consists out of 4 'in city' cycles and one 'out of the city' cycle. As you can see, you can’t call those acceleration times fast So if your car isn't underpowered, those test figures are lower than in real life situations. Also the car manufacturers know this and engineer their cars so that they’re running really eco friendly in the regimes tested by those mandatory test cycles, so they don’t have to put costly exhaust after treatment systems onto their cars to comply with the emission standards.

[TransAm]

Originally Posted by evoWALO Dude thanks for pointing out the diff of UK & US gallons! I got the manufacturer fuel consumption for a UK site. A UK mile is still a US mile? Manufacturer's stated is now 32.1MP(UK)G/11.4KPL

Yes Evo, a UK Mile = a US Mile

In fact a US fluid ounce = a UK fluid ounce (fl oz - a measurement of liquid)

While the standard units are the same, in the UK there are 20 fl oz in a pint and in the US there are 16 fl oz in a pint.

Of course, 8 pints = 1 gallon so the 'difference' carries forward...

[Akmon]

A question for you guys:How do you transform m per gallons in liters/100km?There is a formula?

[Wutputt]

1 mpg (US) = 235 l/100 km
1 mpg (UK) = 282 l/100 km


so for example 30 mpg (US) = 235 l/100 km / 30 = 7,83 l/100 km

[evoWalo]

You can also use google calculator to compute for imperial/us mpg to kpl and vice versa.

For UK: 1 mile per imperial gallon to kpl
For US: 1 mile per gallon to kpl

It also works with l/100km to kpl or imperial/us mpg