Thread: MPG...

first off i ended up resetting the MPG calculator, which i'm kind of thinking was bad idea.. anywho i've only been driving it for a few days and i stay around 15-16... now.. im not sure if thats normal for the first little while of the reset or if maybe i have some type of air leak or what... but im just curious if i should worry about something for now or just give it time.. im getting 270-300miles to a tank not sure if thats great or not. just curious if someone could shed some light on this for me.





Ok.. so i went through some minor calculations and it seems to balance out to about 20mpg but im not sure how much to compensate for reserve. so my question still stands.

Thanks for any help.

First, your mileage is affected by so many things its not even funny. Driving style, temperature, weight, city or highway driving, quality of the fuel, state of the engine and so on.

The problem with the DIC, unless you have an instant fuel economy read out, is that it does not do good in combined driving. Meaning if you do some city driving and then some highway driving, the DIC mpg doesnt adjust well. If you do all city or all highway then it does pretty darn good. My experience in those situations is that it is usually within a tenth or two when I do the calculations by hand but Ive seen it several miles per gallon off when I do combined driving.

Further more, the DIC (again, unless you have instant mpg readout) averages fuel economy. So the more you drive without resetting the less it will change because it is trying to take everything into account. And really, this is ideally how it was meant to be used. If you dont reset it, over time it should come close to reflecting what you are actually getting when you manually calculate things.

Now, if you are getting 20mpg on all highway runs, then Id say there was something wrong cause it is very common for GP's to get upper 20's even 30's with all highway driving. I personally get around 32 - 33 when I drive all highway. All city, depending on how aggressive I am, I'll get 19, 20, 21, somewhere in there. Combined driving, about 35% city and 65% highway I am running about 28mpg.

But just keep in mind when talking about miles per gallon or fuel economy in general that its a fickle thing. The biggest variable I have found in my studies on this was that not everyone fills up their tank the same. The next biggest was the gas pump handle cutoff (vapor cutoff). None of the handles are calibrated the same, even within the same gas station.

So you are much better off keeping track of your economy by doing the calculations by hand and developing a long term history of what your car gets. And by long term I mean three months, six months or more. I have every single fuel reciept since I bought my Grand Prix some 4 years ago. I bought an Isuzu Rodeo in February and I have every single fuel receipt for it. On each receipt I write down the odometer and trip odometer readings. I reset the trip odometer at every tank. Then I will record that information in a spread sheet or something like that. That way I can look back over time and see whats going on.

Anyway, hope this helps out in some way.

Wow.. you have no idea how much you have helped me out. I do most city driving and I am aggressive about 40% of the time. So i will definitely take into consideration about what you've said when i do my calculations thanks a bunch!