MPG

[Cookies]

Was wondering how close you guys actually get to your cars displayed MPG. I have been having fuel economy problems for a while and have been trying to narrow down the issue. My dash displays that i get 22.12 mpg (10.6 L/100km) average. I have gotten this more or less consistently per tank. But I will only get 300-315 KM per tank (50/50 highway city). If the gas tank is 50L that puts my actual mpg at 13 (18 L/100Km).

I have the same problems on the stock tune and tuned. I have changed out all the plugs, new air filter, put that stuff in for carbon buildup, and cleaned the MAF sensor.

My car's alignment is a bit off which is the only con i can think of. I also had a problem with one of my handbrake drum brakes being seized partially on which was effecting my mpg before aswell.

Was just looking for some pointers, im really lost at this point. I also have an OFT which i could record how the car runs but not quite sure what to look at.

Thank you for anyone that helps

[Leonardo]

The dash is not accurate. And, you probably are not doing the math correctly. When I figure out my MPG, I set the trip meter to zero when I fill up, then when I need gas, I go to the exact same pump and fill up. When the pump clicks off, I divide the miles on my trip meter by gallons put into the car.


Also, get an alignment soon. Your car will drive better and your tires will last longer.

[Dadhawk]

When you say "per tank" are you doing the calculations based on the amount of fuel you are adding each time ([Distance Driven] / [Fuel Used]) or are you using "per tank" as more generic, as in distance between fill-ups?

The best measurement of fuel economy is to start with a full tank, drive a certain distance, then refill the tank to the same level. That will give you the most accurate measurement, although it still has some variables.

My experience is the car readout is a bit higher than the calculated readout but not my much, usually within a MPG or so.

By the way, if you are getting 22MPG you must be doing a lot of city driving. My 150,000 mile average is 33.27MPG. If is city driving, it will vary a lot from one fillup to the next and that could account for some of it.

[Cookies]

Originally Posted by Dadhawk

When you say "per tank" are you doing the calculations based on the amount of fuel you are adding each time ([Distance Driven] / [Fuel Used]) or are you using "per tank" as more generic, as in distance between fill-ups?

The best measurement of fuel economy is to start with a full tank, drive a certain distance, then refill the tank to the same level. That will give you the most accurate measurement, although it still has some variables.

My experience is the car readout is a bit higher than the calculated readout but not my much, usually within a MPG or so.

I do it based off the distance driven between fill up's to the same level. I pretty much always fill up at the same fuel level.

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[Leonardo]

Weird. I have gotten over 500 miles out of a tank before. And, avg about 400 miles per tank.

I do have an AT though.

[Dadhawk]

Originally Posted by Cookies

I do it based off the distance driven between fill up's to the same level. I pretty much always fill up at the same fuel level.

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But are you using the actual amount of fuel used to do the calculation? That is the only way to absolutely know. The gas gauge is accurate but it could be as much as one gallon difference and you wouldn't notice on the gauge. Even half gallon variation makes a significant difference in our small tank and you can't tell that from the fuel gauge.


(Also, note the edit to my entry above)

[Tcoat]

Originally Posted by Cookies

I do it based off the distance driven between fill up's to the same level. I pretty much always fill up at the same fuel level.

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Using the fuel gauge to determine "level"? You need to get more accurate readings (as Dadhawk said) since you are introducing to many variables into the test.
As Dadhawk says I have found the mileage gauge to be reasonably accurate to within about half a liter per 100kms. so to have such a large gap between your calculation and the reading means something is off in your method. An 8 l/100km difference is just not possible. In fact the difference in your numbers is greater than my actual average which is 7.4 l/100km.
Your 10.6 is still not great even with the city driving in the mix but not out of the realm of possibility depending on how much stop and go you do and how you do those goes!

[Dadhawk]

Originally Posted by Leonardo

Weird. I have gotten over 500 miles out of a tank before. And, avg about 400 miles per tank.

I do have an AT though.

You must have run the tank close to dry to get that! Best I've gotten out of a single tank is 426 miles at 10.85 gallons which is about 39.3 MPG. If I had run the tank dry I would have been at 521 miles.

Absolute best tank I had was 40.6 MPG. If I had run it dry (13.2 gallons) I would have been 534.6 miles.

[wparsons]

It's already been covered, but you need to look at how much fuel you ACTUALLY put in instead of assuming you completely emptied the tank. I typically only put 40-41L into mine, and that's filling up when the light comes on. You'd have to drive about 100kms with the light on to come close to putting in 50L. Some tanks I'll drive ~40kms with the light on and still only put in 42-43L.

The number shown on the dash excludes idling time IIRC, so if you spend a lot of time idling (or in stop and go traffic), it can be off by a fair amount. If not, it should be reasonably close.

I don't drive mine like a grandma by any stretch, and the lifetime average on it is about 8.5L/100kms, and about 51% highway driving. 10L/100kms pure city is pretty typical. If you're actually getting much worse I'd look at your driving habits.

[Cookies]

Originally Posted by Tcoat

Using the fuel gauge to determine "level"? You need to get more accurate readings (as Dadhawk said) since you are introducing to many variables into the test.
As Dadhawk says I have found the mileage gauge to be reasonably accurate to within about half a liter per 100kms. so to have such a large gap between your calculation and the reading means something is off in your method. An 8 l/100km difference is just not possible. In fact the difference in your numbers is greater than my actual average which is 7.4 l/100km.
Your 10.6 is still not great even with the city driving in the mix but not out of the realm of possibility depending on how much stop and go you do and how you do those goes!

So here is the info from my last tank. I drove it like a baby the majority of the time and never really went above 4k rpm. Legit just filled it up.

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[Tcoat]

Originally Posted by Cookies

So here is the info from my last tank. I drove it like a baby the majority of the time and never really went above 4k rpm. Legit just filled it up.

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OK so that is about 10.6 l/100km. Just like your gauge says. Not great but far better than the 18 you were calculating.

[Dadhawk]

Originally Posted by Tcoat

OK so that is about 10.6 l/100km. Just like your gauge says. Not great but far better than the 18 you were calculating.

As an aside, I never tried to do l/100km before.

Geez, who came up with that being a good way to do it! I guess once you get used to doing it you can do it in your head, but MPG or MPL sure is easier!

[Cookies]

Originally Posted by Tcoat

OK so that is about 10.6 l/100km. Just like your gauge says. Not great but far better than the 18 you were calculating.

Yeah I'm going to have to record some time on the highway as this should be close to the average city mpg of the car. I don't think I could drive it more conservately than I did either and it was 50/50 highway and city. So I still feel like it's off.

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[Tcoat]

Originally Posted by Dadhawk

As an aside, I never tried to do l/100km before.

Geez, who came up with that being a good way to do it! I guess once you get used to doing it you can do it in your head, but MPG or MPL sure is easier!

I am old enough that I am bimeasuremental.


Besides it is the readout our cars have. I have to convert to MPG.