I don't always feel like emptying my gas tank and then filling it up completely just to get an accurate average MPG calculation, it's also impossible for me to drive an entire tank without getting into the secondaries I can't help myself. That would just be a waste lol, after all my Duster is my "fun" car.
Easiest way to keep up with fuel mileage is to download an app like Fuel Manager and simply log the mileage and gallons every time you fill up and it will tell you your mpg for that tank, as well as a running average mpg of every time you filled up.
If you want to just figure it up by hand once, there’s no need to empty your tank. Simply fill up your tank and wrote down your odometer mileage. The next time you fill up, decide the gallons by however many miles you drove on that tank of gas, whether you used 1/4 tank or 7/8 tank doesn’t really matter.
