Ever burned a cooking pot? The burned food sticks like crazy-sometimes you can only remove it by sandpapering the surface. The same is true with engine oil-if the oil breks down, it will attach itself to the interior engine surfaces and stick to it.
By the way, has teflon ever been used to coat engines? It would seem that this would prevent a lot of oil failure problems.
Teflon has a melting point of a bit over 600 degrees F. I don’t know how hot the interior of an engine gets, but I’m sure it’s considerably hotter then that. So I don’t think that would work.
IIRC, even the exhaust manifold runs in the 600 degree range. ISTR, that an O2 sensor needs to get up to 600 degrees before it operates properly. That would imply that the combustion chamber of an IC engines runs well above 600. I mean, there’s fire in there. You can burn Teflon off your pan just by leaving it on your stove too long.
Here’s a Hot Rod magazine article from 2009 detailing the uses of PTFE and other internal engine coatings.