I had a tech put Marvel Mystery Oil in a Pullstar 8000 pneumatic winch air line drip-feed for the gangway on my ship; it swelled the rubber, including the check-ball controlling the pneumatic brake, jamming it on; I had 20 hours into tearing that stupid winch down TWICE before I found the problem.
Another tech put it into the crankcase of a 20,000 psi Hydroblaster, in place of the required Mobil 1. Ugh.
Not a fan of MMO... Smells nice though!