Have you ever notice about this? When you pump a tank full of fuel, the fuel indicator will just stay there for some time, then it drop faster than it was in Full earlier. Have u ever think what is the reason behind this?

Actually the theory was similar to our toilet flushing tank system. It has a float to determine the current water fill level. Once the float reach the top, water will stop flowing into the flushing tank. In our fuel tank, they use similar system whereby the float is the indicator of the fuel level.

Now imagine your fuel is full up to the top of the cube-like tank. So your float will now be stucked at the top of the tank with the float flooded by the fuel itself. Your fuel indicator will show full of course. What if your fuel is now used, let say down to partial of the float is still flooded? Your fuel indicator will still show Full due to the float is still stucked at the top.

Until your fuel is low enough to move the float down, the same goes your fuel indicator. This is basically the theory behind this mystery.