How to Calculate Gas Mileage (MPG) The Right Way

Why should you calculate gas mileage?

Calculating gas mileage is important. Not only so you can get an accurate picture of fuel economy, but also spot potential problems with your car/truck. If fuel economy is a lot less than it’s supposed to be- contact your preferred service department.

Photo by Tim Mossholder

The mpg display in your vehicle might be wrong

To make your gas mileage better, you need to know what you are getting in the first place. Most modern vehicles nowadays will have a digital readout. Probably a display on your dash of the mpg (miles per gallon) you are getting. Ie. How many miles you can drive using one gallon of fuel.

This number will vary from about 6mpg to 60mpg depending on the vehicle you drive.

The number that is displayed on your dash may not be exactly correct.

Just like a trip computer, these can also be reset. This results in false numbers or erratic driving may also skew the results. Some vehicles may also have an instantaneous mpg readout, which is helpful in bettering driving habits to increase mpg. It’ll tell you’re getting about 70 mpg when you coast. So how do you know what you are really getting?

Gather the data to calculate mpg

Do it the old school mathematical way. Calculators are allowed this time and the only person marking your answer will be you!

Fill your fuel tank (to the pump cutoff level)
Reset the trip computer
Drive until fuel is required
Fill the tank again (to the pump cutoff level)
Make a note of the number of gallons used to re-fill and the miles on the trip counter
Reset trip
Use the formula below to calculate mpg using your numbers
Repeat this four or five times to give you a good average