
I always keep a record of my cars, in terms of anything I do to/with the car. As you can see I record all of the stats at each fill up, you will notice that with similar driving, of course cant be the exact same, my MPG is slowly going up as my engine is breaking in. This is nice to know as the MPG currently blows...
My carputer is currently showing 15.7 mpg after 140 miles on my current tank, however for the records I use actual MPG (actual miles and actual gallons burned).
If anyone wants the excel file to use for yourself, just ask. Its nice to show someone when selling a car, your exact records of oil changes and service and whatnot... plus its interesting over time ; )