so about a month or so ago i had my car sitting outside (low 90's), when i exited my car i had about 3/4 tank of gas. when i started my car back up a few hours later the gas gauge went back to a full tank. after driving it for about an hour, it quickly went back down. today, same thing happened. about 3/4 tank again, washed my car (low 80's outside) and when i started it backup, almost full again. the reason i included the temps was to show that i dont think it is heat creating pressure problem. any suggestions or has anyone experienced this before?

 

Test your fuel sending unit. I'm sure the FSM will list the voltage range. Just use some aligator clips to hook the leads of a DMM up to the wires on the sending unit and sweep the arm through its range. Be gentle, you don't want to bend it.