[throwaway2037]

    > they go rancid pretty fast

How fast is "pretty fast"? I assume that most restaurants change their fryer oil at a max once per week. And after cooking, the (underlying) food is more likely to spoil before the oil on the food going rancid.

[majkinetor]

You should assume the worst. Even if oils are not smelly, they can be spoiled and nobody will give a damn at the restaurant.

Fast like you use it once or twice, it goes rancid.

I witnessed restaurants in the Meditterian that keep oils on the tables for salads, and they are rancid due to hot temperatures.

Cook on coconut oil or palm oil, they are the most stable ones. If you go with plant oils, use olive oil as it seets in between poly and saturated oils.