This thread got me wondering about MMO, so I did a little surfing and came up with the following info:
Marvel Mystery Oil - Moyer Marine Atomic 4 Community
Slick 50 and other ail additives
I used MMO while rebuilding my FE and it did seem to "stick" fairly well to the bores. I haven't and probably won't run it in my engine, since I agree with some of the observations in the attached. Those being that in the crankcase I believe it will affect the viscosity and temp qualities of my
oil and I see no advantage in running it thru my fuel system and would tend to think that "burning
oil" with fuel would cause deposits. I would suggest using a fuel additive formulated for cleaning as an alternative.
Just my opinion,
Mike