You need to check the lenght of your fuel pickup tube and see if it goes to a couple of inches from the bottom of the tank. Easy to remove, stick something clean in there and compare. Also, when your gage says empty, visually check the fuel level and figure the volume of the tank(remaining fuel) to see how accurate the gauge is. Be sure that the fuel pickup tube doesn't go all the way to the bottom, it will pick up trash and water if it goes to the bottom. Engine hours and comsumpion at crusing speed are the best way to keep up with it as someone has already said