It is your fuel sending unit, locating on the fuel pump assembly inside the tank. If you are cheap, err. I mean frugal like me, just fill up the tank to complete full, reset the trip odometer, and drive to about 250 miles, and refill to full tank again. Or whatever mileage that you know a full tank can get you less 50 miles, just in case. I did this for two years until I finally replaced the sending unit.