you stress MPG as mileage|price|gallons, my family provides me mileage|price|gallons when they fuel up, and the mobile site asks for input for mileage|gallons|price. This leads to some extremely good rates, until I realize what has happened again and then have to go edit the input. Otherwise - OUTSTANDING SERVICE!
If I'm standing at the pump, entering the data as I fill up, I will enter the mileage, then the price per gallon. Once the pump auto-stops, I enter the number of gallons.
Seems to me a fairly typical use case and would warrant the reordering of the form fields.