Just another oil additive.
In 1976, STP faced a consumer protection order that required it to have scientific backing for certain statements and prohibited making false claims. In 1978, it paid a $500,000 civil penalty over claims. In 1995, STP paid $888,000 to settle Federal Trade Commission charges of false advertising.
Sorry, but yes, it is worthless crap. At least they could have bumped up the zinc and phosphorus and sold it as something that could replenish viscosity half way through a change. What are their marketers smoking? Thanks Project Farm and the OP.
I remember using STP when I first started driving , really didn't know if it did any good or not but was told I should use it...so I did...I haven't really noticed and STP in the stores or auto parts places but then again I wasn't looking for it...I do remember having a lot of the STP stickers though ...lol