>From a technical perspective, Teflon has a high concentration of chorlides in it, which can help induce stress corrosion cracking (a bad thing). I doubt if that would be much of a concern in any automobile system, but in any system of high stress (thernal, especially) you will find that halogens are prohibited for that reason. Come to think of it though, I would not use a anti-sieze compound that has a halogen derivative component (chlorine, bromine, etc) on intake/exhaust manifold bolts/studs or any other fastening device internal of the engine. The stainless steels are especially susceptible to halogen-induced stress corrosion cracking (SSC). Has anyone had an exhaust manifold bolt head twist off while removing? The failure mechanism could very well be SSC not simply the surface rust that you see. DO NOT count on NAPA, PEP BOYS, etc to sell only the compounds that do not have halogens - check for yourself to be safe. I seem to recall one of the Nevr-Seez products was halogen free, but not all - so be careful for long term's sake. Fred 6894