How to calculate average miles per gallon

The most accurate way to calculate average miles per gallon

This article shows you how to calculate average miles per gallon in the most accurate way. You can’t rely on the MPG calculator in late model cars is often inaccurate because it’s an estimation based on a rough calculation of how much gas you’ve used. But the remaining amount of gas is determined by the fuel sending unit in the tank and it simply isn’t that accurate.

Fill the tank, but don’t over-fill

Fill your gas tank at the pump until the nozzle clicks off. Stop at the first nozzle click. Don’t keep filling or it will throw off your calculations. Reset your trip odometer to 0. If you don’t have a trip odometer, write down the mileage after filing your vehicle.

Drive in city traffic until your gas tank is near empty

Follow your normal driving patterns for city driving or a combination of city/highway driving. Don’t change the way you accelerate. This is critical to getting an accurate read on your gas mileage. If you change your driving habits during the test, you won’t get an accurate miles per gallon figure.

Refill the tank the same way

Fill the tank again, stopping when the nozzle clicks off. Do not continue to refill. Note how many gallons it took to fill  your tank.

See this post to learn why everyone gets lower gas mileage in winter

Divide the miles driven by the number of gallons needed to refill

Using the mileage from your trip odometer, divide the miles driven by the number of gallons needed to fill the tank.

For example. Your trip odometer shows you’ve driven 327 miles since you first filled the tank. You added 16.5 gallons. 327 ÷ 16.5 = 19.18 miles per gallon. You now have your average miles per gallon for city or city/highway driving.

Repeat the test on highway trips to get your highway MPG

Fill your tank and take a long trip. Then perform the same calculation. This will give you

©, 2023 Rick Muscoplat