RE: Fuel Gauge not reading accurately
I agree with NovaResource that this could be a bad ground wire connection, especially since the gauge jumps up and down between fills. Old style floats with leaks would sink and then drain as the gas was used up to refloat briefly when the tank was filled, but that's not the symtoms you see. Most newer floats are made out of a closed cell foam that I've never seen develop a problem (but all things are possible I suppose). I'd start by check the ground wiring to the sending unit.