I get the low fuel warning to soon I think. Each time I get the warning I drive another forty or so miles. When I fill it up I can only get 15 gallons in it. It is a 2007 X Auto with 4.1 gears and 17 inch tires. It is supposed to have 18.5 gallon tank. Am I wrong on the tank size? I guess I will have to take a spare gas can with me to see. If the gauge is wrong, can it be reset?