Choose a frying oil of good quality. With the FRITEL Turbo SF fryers, you can also use fat. In between two fryings, never leave the fries above the oil, as this will make them soft. For taste as well as for health, it is best to change the oil regularly. The oil should be changed when it starts to darken, becomes thicker, and begins to smell, which is typically after about 10 fryings.