[Brock]

instead of doing the how far did i fill up routine each time...either here or blue forum someone gave me a spreadsheet with formulas already in it for miles per gallon calculation.

you put your starting mileage on first line and it already has tank size and such. Each time you fill up you then take note of:

1- air temp
2. miles on odometer
3- octane pumped
4- gallons pumped
5- price per gallon
6- gas station brand
7- notes for items like towing, air conditioner, or excessive speed that might impact reading

then next time you fill up you do same thing and it computes mileage based on what you reported earlier versus this fill up....i recommend trying to use same pump and going with first cutoff each time unless you can visually see it at neck each time.

Not perfect or as good as onboard system but pretty nice.....