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Summary: Find the actual gas mileage of a car requires dividing the miles driven by the gallons of gasoline used, which can easily be done by filling up the car, resetting the odometer and reading the mileage when the car runs out of gas. Calculate true gas mileage of a vehicle with instructions from an ASE-certified technician in this free video on cars.
John Robey is an ASE-certified technician with an associate degree in automotive technology. He has more than six years of experience as a technician and more than four years of...read more
"In this clip we're going to discuss how to calculate the actual fuel mileage that your vehicle is getting. It's pretty simple, really all you do is you take the amount of gasoline that you're going to put into your car when it's empty; in this case let's say we put in 10 gallons into a vehicle and you run it on empty you got 400 miles on that 10 gallons you're getting 40 miles to the gallon. So sensibly all you do is you take the actual mileage you've driven on the amount of gasoline and you divide it by the amount of gasoline you put into the vehicle. Most people want to reset your odometers so you don't have to write down your mileage every time you get gas, and it's also important to try and keep a log book whenever you are doing this."
eHow Article: How to Find the Actual Gas Mileage of Your Car