I'm embarassed to say, but this is the inside of my gas filler door. It probably hasn't been cleaned in 13 years. I tried to clean it today with a cleaner wax, but there appears to be some kind of thick film covering the door. I'm not too worried about rust in this area because I'll be keeping it well cleaned. I tried to clean it with an all purpose cleaner, but that did nothing. Any suggestions would be greatly appreciated?