GasMaster!

GasMaster is meant to allow you to log all your fill ups for all cars you own.

Each time you fill your tank, simply record your total mileage, the amount of gas you bought, and how much the purchase cost. GasMaster will calculate and track how far you drive between each fill up (trip mileage), your historical minimum, maximum and average gas mileage, cost per gallon, and cost per mile driven.