To add: mixing in this oil is almost guaranteed to cause all the suspended shit in your oil to drop out. The viscosity of the oil when it is cold is lower than that of the engine oil when warm. Cooking oil burns at a fairly low temp. Like https://lemmy.ca/u/[email protected] said it would only really get you to the shop. Your rings would scrape, your bearings would be at a high risk of metal to metal contact, the quickened aging process would start right away and excess carbon would be a sudden issue. The engine would not be able to dispose of its heat very well, due to issues with the oil, and be at risk of overheating. Depending on how the cooling system is set up, it is at a higher risk of failure that would put water and oil into contact, which isn’t good. Also, it could cause varnishing in certain internal oil galleries, which would cause a series of issues and failures.