How anal is VW when it comes to the warranty on their new cars? Can you pop in a K&N filter and not have them void your warranty? I know this is a dumb question, but I don't know how new car warranties are these days. Apparently a guy I work with said that Honda says that he can only use Honda-certified oil in his 03 Accord in oil changes or else they'll void his warranty. Can someone fill me in?