Interesting story; thanks for sharing.
I've noticed Marvel Mystery oil on the shelf of auto parts stores since the mid-60s, but never felt the inclination to ever buy it. I don't think I could ever get past the name. Nothing rings of snake oil more than the words "Marvel" or "Mystery " in the name. Well, unless it was preceded with some doctor's name like, "Dr. Tinker's Marvel Mystery oil". Now wouldn't that be a fun name?
All joking aside, I just have never bought a can/quart and have always wondered about it.