To be fair: restaurant-style deep frying involves keeping oil hot for long periods of time, and more unsaturated fats are less stable. All these cheap seed oil

To be fair: restaurant-style deep frying involves keeping oil hot for long periods of time, and more unsaturated fats are less stable. All these cheap seed oils are quite high in polyunsaturated fatty acids, they often (AFAICT) have preservatives added to try to stabilize them, and all the papers suggest that frying oil that’s been used for a few hours contains lots of stuff that is not present in fresh oil. If you want good performance out of an unmodified oil from a plant, you end up with peanut oil (a bit more expensive) or something like avocado or coconut oil (very expensive). Seriously: go shop at a restaurant supply site for frying oils, and you’ll discover a lot of options like “soybean oil based”. Or you can use animal fats. And competently-done deep frying doesn’t result in much absorption of the oil into the food. But, as the oil polymerizes, it gets stickier and more ends up in the food. (Yes, those apparently healthy oils, high in polyunsaturated omega-3 fatty acids, are even unstable at room temperature. Old flaxseed oil is sticky and utterly disgusting. Old canola oil is not quite as nasty smelling but still rather sticky.)