Oil Additives - thumbs up or down?

[TheEdgeofSanity]

I am already predicting thumbs down but there is one brand that has me wondering. My dad swears on "Slick 50" - in the days before synthetic oil was widely available to the general public, we owned many many GM vehicles because my dad could buy them with his GM discount, drive them for a year, and sell them and make money. Every single vehicle got a Slick 50 treatment and it seems to have at the very least not hurt any of the engines. Some of our vehicles were sold to family members who still drive them to this day. My uncle bought our 1993 Chevy S-10 with the 4.3 v6 and kept up the slick 50 treatment and he now has over 400,000 on the original stock internals. Our 92 Lumina is also still on the road with well over 200K, belonging to a family friends son who beats the piss out of it. So question, does this stuff actually work? It appears to but I don't know whats in it that is it's "active ingredient" or whatnot?