Newbie wrote:
> It may seem like a superfluous question, but what is the best way of
> calculating what mmg yuor vehicle is getting? I have my miles reading
> of course, and I can record how much gas I put in, but there was some
> gas already there in the tank, and how do I know what was traveled on
> how much gas? If you have a good system, please share!

Start with a full tank.
record mileage.
Drive.
At next fill, record mileage and the gallons to fill back up.

With my truck I just go to the first click. Your mileage will vary
depending on the type of driving, the weather (-40 idling uses a lot of
gas) etc etc... so just keep tracking it.

I use a spreadsheet and track the average and the average for the last
10 tanks. I found the last 10 tankfuls to be a good indicator of my
overall mileage. I moved to a more rural area so I spent less time in
rush hour so the average mpg went up by a couple, but went back down in
the winter... and went up a couple mpg when I finally changed the plugs
and did a tune up.

My truck usually averages around 12-16mpg with the odd highway drive
above 20.

Why the average? Because unless you drive the same road under the same
conditions at the same speed with the same brand of gas filled to the
same spot in the tank you're introducing all kinds of "error" into the
equation. Averaging that over 10 tanks will give you a more "real
world" mileage.

If you have excel I can email you a copy of the spreadsheet...
Ray