How to Calculate Gas Mileageby eHow Contributor
In days of long commutes and climbing gas prices, consumers are taking note of how many miles per gallon (MPG) they're getting. New vehicles often come with a sticker indicating gas mileage, but that may not be accurate for your driving patterns. Follow these few simple steps to calculate the actual MPG for your new or used vehicle.
Fill the gas tank completely. Write down the mileage on the odometer reading before leaving the gas station.
Create a log to record the mileage and number of gallons every time you fill up. Keep it in an easy-to-access place, such as the glove compartment.
Refill the tank to the top, when it's time to refuel, using the same grade of gasoline as was used during the initial fill. Log the number of gallons required to fill the tank and the odometer reading.
Subtract the previous odometer reading from the second to calculate the distance driven.
Calculate the miles per gallon by dividing the number of miles driven by the total gallons of gas it took to fill the tank the second time.