I read a book called "things your mechanic don't want you to know" about scams in the auto repair industry (Sears, Midas, small independants etc.). He he had a chapter on additives, and he said that Slick 50 is the only one with the right chemical balance to take advantage of the Teflon in it.

Then I read somewhere else where they tested all these cabs in NYC and gave a group Synthetics, another group regular oil and the last group additives (Slick 50, Duralube etc.) they said there is no difference as long as the oil changes are kept up at a regular interval.

I think I'm going to switch to synthetics.