Hi Guys, I own a 2006 Chevy 3500 1 Ton Dump . Last week on my way to work the tighten fuel cap warning came on . I pull over and find my fuel cap is barley on . I always tighten it the best I can because I had a problem with the check engine light coming on for a loose fuel cap. Then the next morning I checked it and it was barley on again! I'm worried someone put something in my gas. The truck seems to be running ok . But now I'm paranoid. Its there anything that could've been put in the gas that takes awhile to ruin your engine?