Many car, truck or sport-utility vehicle owners want or need to keep track of their vehicle's mileage. While fuel economy gauges, which allow drivers to see their vehicle's current miles per gallon at a glance, are standard in 92 percent of 2011 model-year vehicles, most vehicles on the road do not have them. You can calculate your vehicle's mpg by recording the number of gallons of fuel you purchase, keeping track of your mileage for each tank of gas, either by hand or with a trip odometer, and doing a bit of elementary math.
Fill your gas tank completely, until the hose shuts off automatically. Write down the odometer reading before you leave the gas station. As an example, if the odometer reads 14,203, this is the number you write down. Label it, and put it in a safe place, such as the glove compartment.
Drive as you normally do until the gas tank is close to empty. Leave enough gas in the tank to get to a gas station to refuel.
Refill the gas tank completely. Write down the number of gallons you pumped into the tank and the new odometer reading. For this example, you bought 12 gallons of gas and the odometer now reads 14,347.
Subtract the first odometer reading from the second one. In the example, this is 14,347 minus 14,203. The answer is 144. This tells you how many miles you drove on that tank.
Divide the number of miles you drove by the number of gallons you pumped into the gas tank at the second fill up. Continuing with the example, this is 144 divided by 12. The answer is 12, which is your vehicle's mpg between the two visits to a gas station.
Reset your trip odometer at the gas station. Fill your gas tank completely, until the hose shuts off.
Drive as you normally do until the gas tank is close to empty, then head to the gas station.
Fill the tank completely. Write down the number of gallons you pumped into the tank and the mileage indicated on the trip odometer. As an example, use 12 gallons of fuel and a trip odometer reading of 240 miles. Reset the odometer if you want to check your mpg again.
Divide the number of miles you drove by the number of gallons you put in the gas tank. In the example, this is 240 divided by 12. The answer of 20 is the mpg your vehicle got on the previous tank of gas.
