DuPont stopped selling their PTFE to folk using/blending/adding it to things DuPont didn't think it was suitable for, got sued for it, and ended up resupplying them. As I recall.
Way back in the day, the funniest I thought was Briggs & Stratton. They both sold slick-50 as a B&S endorsed product, and denied warranty claims on failed engines if slick-50 was used in them. Made working in the mower shop kinda interesting.
Way way back in the day, I tried a seal sweller stop leak because I was desperate. Strange product who's name I've forgotten, and I've never seen it again. It was like sand in a can. Instructions were weird, having you slowly pour it into the engine while driving it, or something like that. Anyhow, it worked. Some time later I had to open that engine up. The stuff had packed around the leaking seals, creating a mechanical barrier, stopping the leaks. Wasn't anywhere that there hadn't been active leaking.
Remember the shim stock behind worn bearings? God I hated running into that.
