I have mixed feelings about slick 50. I used it in my mitsu when I first got it (after break in) then again at 50k miles but not after that. Didnt hurt anything (had 143k on it when I sold it) but dont know if it helped. When my dad got the engine in his olds rebuilt (professional race engine shop) they said not to use it till after 10k miles break in cuz the stuff does work and the engine wont break in properly if used before then.

Others including dupont (inventers and makers of ptfe) say it does nothing and may even cause problems. So I dont know.

I do know I will never use STP in my engine. It will form little balls of gummy junk in the oil pan. I've seen that several times. For now I'll just stick with mobile 1 and sea foam cleanings.