@Felthry Motor oil to fry things is bad because it isn't Just petroleum oil. And even if it was, it's poison.
Using vegetable oils in an engine is a well known phenomena. In diesels as Fuel, and some oils like Peanut oil and Castor bean oils are fantastic engine oils, in their specific application.
@Motodrachen yeah i was thinking motor oil tends to have additives that are probably even more poisonous than the petroleum oil itself