The best oils for deep frying are canola, safflower and peanut oils. They have a high smoke point, which is the temperature when the oil starts to break down and burn, and can handle the high temperatures required to deep fry.
Canola and safflower oils have a neutral flavor that do not affect the flavor of the food being fried. Canola and safflower can be used for savory or sweet frying, such as chicken, tempura, or crullers. Peanut oil, however, gives the food a slightly nuttier taste as well as a darker color. Peanut oil is favored for frying doughnuts because it complements the sweet nature of the doughnut's batter.