I have a 2006 F-150 XL with only 24,500 miles on it. (Have a work truck I drive the hell out of). Anyway, every once in a while from my Ford I hear what sounds like a knock or a ping kind of like in an old car and you use low octane gas. I don't know if it's my imagination or if it's something that I need to investigate? I'm not losing acceleration or power so I don't know? Anybody have any ideas or simply tell me I'm crazy thx!