its not crap. it was made for servicing marine equipment
OP marvel mystery oil works good also
Its crap in a can. King of the snake oil.
Its naptha/IPA/light oil. Google the MSDS from 2010, before they changed the MSDS to protect trade secrets.
You know all the evil alcohol everyone is blaming for everything going wrong with gas powered equipment, especially marine engines, it's in Seafoam at about 10-20% by volume. Thats more alcohol by volume than what comes out of the pump. Slightly different chemical make up between IPA and fuel ethanol but its still alcohol and has all the negative properties.