OK, but read this even if you're thinking about using any of those BS products:

http://www.geocities.com/chrislonghurst/engineoil_bible.html#blackdeath

Looks like "the big 3" were finally busted. Too bad there's still a few zillion left to weed out and more suckers biting on them everyday.

Most of them survive because there's many people with junkers who will try any bottle remedy in the hope that "just maybe" it'll help their tired old POS engine, especially if it's being sold to some unsuspecting buyer and $3 is far cheaper than an engine overhaul.