My 2001 3.0 started doing this about 8 months ago. It only happens when I let the fuel level drop below 1/4 tank. When I refuel, the gauge only comes back up to 1/4 tank. It comes back to full after a drive and cycling the ignition a few times. It has gotten worse with time. I'm sure I will have to eventually replace the sending unit(s). It is quite an expensive repair especially for the purpose it serves. I will definitely not deal with it until the gauge fails completely and even then I might just stick with the trip meter.