I know there is a webapp that does the basic calculation for the Fuel Economy and keeps a running history.

But here is my dilemma. I don't have stock tires and my Speedo is off. I know how much in percent.

Would others find use in a MPG program that you can enter the Mileage on the Trip Odometer, the Gallons, $ per Gallon, and the "adjustment?"

I have a spreadsheet built in Excel, but figured someone with the expertise to make it look pretty on the iPhone could make something useful. For Tuners, Offroaders, and soccer mom's.

I was hoping if someone was feeling kind they could build it so it sends the info to the "home" computer so more detailed info can be recorded.

If someone would like to see the Spreadsheet I use I can send you the link, because I found it on an Offroading site and modified it a little.