Ever since I bought my truck, the gas guage has never worked right. When the tank is full, the guage is on 1/4 tank. When it is empty, it sits about 1/16 inch below E. And, it appears to move in a relative rate in that range. Kind of like it is just operating on a much smaller scale. How can I determine if it is the guage or the sending unit? I don't think its the float in the tank as it doesn't sit on 1/4 for a long time and then drop. It starts dropping immediately when I start eatin' up the gas.