I just found the Fuelly app, and what a great idea! Yay, no more scribbled-on gas receipts floating around in my car. Now I can get some real data from it all over time. Very happy to have come across this!
I scribble on gas receipts then enter the data into Fuelly (via desktop computer) then put the receipt's back in the car. An I nuts or what (don't answer that)