If the gas cap is the cause of a CEL, it will go out by itself after a week or so. Brought mine into the dealer the first time this happened and this is what he told me. Had it happen again and just ignored the light for a week and, indeed, it went away. For the most part, as long as the gas cap is secured after filling up each time AND you don't run the car extremely low on fuel, the light won't come on. The 2 times it came on for me both involved running the tank down to less than 2 gallons.