RE: Marvel Mystery Oil
Although there are some on this list that use MMO in various ways there is
little or no need for such with today's detergent oils.  If you had an
engine that had been run way to many miles without an oil change then maybe.
I have personally seen internal parts from a WBX (valve lifters) badly
scored or actually worn through from an engine that had run MMO all the
time for many thousands of miles.  Was MMO to blame? Maybe, maybe not.  But
since it thins out the oil in the engine MMO was a suspect in that case.