Calculate fuel mileage by dividing the amount of miles traveled by the gallons used. Make sure you reset your odometer after refilling your tank. On your next refueling, note the gallons used.
- Prepare your vehicle
The most accurate way to determine gas mileage is to run your vehicle until it is completely out of gas. Doing this requires using a 1-gallon gas tank to refuel your vehicle just enough to get to a gas station.
- Run your vehicle out of fuel
By completely running your vehicle out of fuel and using a 1-gallon can to get you to a gas station, you have a very accurate way to measure your mileage. If your tank holds 16.9 gallons and you fill it with 16.7 gallons, you know that you have 16.9 gallons in your tank because the missing .2 gallons is from the one-gallon gas can. Make sure to reset the travel odometer after filling the tank.
- Measure and calculate
Once your vehicle is completely out of gas again, simply look at your miles traveled, and divided it by your tank size (miles travel ÷ tank size = mileage).