[stng87]

I think its because when you fill the tank up, the gas levelof course raises the float to the top of the tank. But then the gas level rises even further to where the gas also hits the top of the tank and submerges the float.
Then as you burn the gas off, the gas level has to first fall to the level of the bottom of the float before the float can begin to fall. Until then, the guage reads the same full reading. So the gas level can fall like 1- 3 inches,depending on the size of the float,(I dont remember) before the guage is ever affected.
What really annoys me is when my guage sometimes reads half when its really at 1/4. Or worse when it's empty! @#$% gas prices.