I was told by someone not to put a gasoline stabilizer in the gas because it would make the car run very sluggish until I use all of the gas. I just filled the car with gas to keep moisture out of the tank. Is there a way to determine if it is a fuel injector or a stuck lifter. Also I have been told not to put any additives in the oil. If I did would it void the warranty or cause sludge build-up? I really don't want to take it to the dealer if I don't have too. Most mechanics don't take extra care not to scratch your car. When I had the fan recall repaired they put a scrape in the air cleaner cover. I understand you can force them to repair the scratch but I would rather not have a repainted fender.