I turned the car on and off a few more time throughout the day but it kept reading full. I know I only had about a half a tank. Well, this morning when I went to the store it still read full. When I came out from getting my stuff I turned the car on and it went back to normal. Everything else was working fine. My speedometer, mileage counter, oil gauge, and temperature gauge. Does anyone have a clue why this might have happened and if I might encounter it again?