How to Figure Gas Mileage?

Fill up your car and write down the mileage. Drive until the next time you need to fill up, fill the tank and write the mileage down again and subtract the 1st mileage from the second mileage to get the number of miles you have driven on that tank of gas. Next divide the number of gallons it took you to fill up the 2nd time into the number of miles driven and this is your gas mileage.