I've ofter wondered if Marvel Mystery Oil was really good for anything. Any info?
Well, I'm obviously not Doug, but I know the answer to this one!
IMO, MMO is the best thing in the world for air tool lubricant. Back in the 80's, Snap-On brand air tool oil was repackaged MMO. It's been a while since I've been able to afford Snap-On tools, so I don't know if they still use MMO or not.
I worked for some years for a place that did lots of steel fabrication as well as industrial tool sales and rentals. We were an authorized Ingersol Rand dealer and repair center and what we used and recommended for all our air tools was MMO. It lubricates very well and it helps keep tools free of the gum and varnish that I've seen build up in some air tools that used "other" air tool oils. I've got an Ingersol Rand angle die grinder that I bought in 1981. It's been used and abused more than you can imagine and I've been through easily a thousand 4" cut-off wheels with it. It doesn't get oiled nearly as often as it should (I hate inline oilers), but it's survived for 27 years on a meager diet of MMO. I've never replaced vanes or even had it open yet and I really do use the crap out of it..
That's what MMO is good for. I buy a gallon of it every couple of years.