My Contour holds a little over 12 Gallons when close to empty. I never let my Contour get below empty because I hate to run out of gas.
The way I figured my MPG is I filled up with gas, write down the odometer mileage, then when my tank is almost empty and I fill up with gas. I then divide the miles driven by the number of gallons of gas that it takes to fill it up. Would that give me the correct MPG?