In the FREE version, we calculate your fuel savings based on US national averages for the cost of gas, electricity, miles per gallon and your estimated commute. Depending on where you live and what kind of car you drive, your fuel savings will be less or more. Upgrading will use the location of your phone to get local prices and you'll be able to enter the year, make and model your current car as well as your commute. While these values are determined automatically, they can also be changed if desired.