[rotorwrench]

It's been used for years on the A & C series Continental engines for the old light single engine airplanes. It would keep the valves from sticking and reduce problems with the higher lead content of 100LL Avgas. Valve problems went away using it back in the 40s. It works well enough in all the various flathead engines as well. It has to be used properly in aircraft engines though. A few folks that have put too much in have payed a high price. Some folks think that more is always better but the stuff isn't fuel.