I have a 97 Honda Civic, I have around 117,000 miles on it. I was driving home and when I was close to home I thought I smelled gas or something in my car and I happened to glance at my gas gauge and it was up at full but I used at least a quarter of a tank of gas then as I was watching the gauge it went back down to where it should be and moved a little bit but not much. It moves a little normally, but never like that before and the smell made me worry.
The smell is a real question but personally I would follow the line from the tank to the injector rail and back to watch for leaks. Then I would suspect the fuel sender for the hankipanky of the moving gauge.