is a spreadsheet I have worked up that calculates MPG and a bunch of other handy stats if you keep a fuel log. I cleared out all but the first ~25 or so entries. ($1.479! Anybody remember when fuel was that cheap?!) The only problem is that I don't know how to make formulas automatically go to the end of the sheet, so as you add data you need to update the formulas to include the new data too. Kinda sux, but I don't know enough about excel to do any better..
Anyhow, someone at ORR asked for it, so I figured I'd post it here too.
I keep a paper & pen log-book in my truck. Every few weeks, months, or whever I feel the urge I bring it into the house and add the new data as needed.