I used it years ago in my Harley Davidson Sportster, had to lower idling after treatment as was mentioned in previous post due to lower friction.

I used it in a few cars years ago without any ill-effects. It is supposed to last for around 50k miles. My dad treated his Cavalier twice and now has just under 300k miles without any motor work done. Not saying this is why his engine lasted...just noting the facts.

I never used it in my VX for two reasons:

1) owner's manual mentioned not adding any oil additives. wanted to not do anything that might void my powertrain warranty.

2) I saw someone criticize slick 50 by adding it to a test tube and heating it with a bunson burner, which caused it to coke up. This left me with the impression that if you treated your engine and it later overheated due to some cooling malfunction...it could "coke-up" and cause issues.