I used it to coat the bore, pistons/rings when rebuilding my engine. Plenty of folks use the old standard, motor
oil. Gessford uses Marvel Mystery
Oil instead, so I followed their lead. Some 4,000 plus miles later, no problem.
Several folks commented about how crazy that was. I figured if Gessford Machine was THE "Machine Shop of the year" a few years back, they must have a clue.
I've been using it as a cylinder/piston installation process ever since. Including small engines, two cycle and four cycle. Most recent application was a 1962 Austin Healey 3000 6 cylinder engine (runs good)!
I don't use it as an additive following a rebuild, I prefer just regular
oil (with EOS or a
Zinc additive for initial breakin due to camshaft considerations).