- Chose a frying oil of good quality. With the FRITEL Turbo SF fryers you can also use fat.- In between 2 fryings, never leave the fries above the oil, 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 and becomes thicker and when she starts smelling. (more or less after 10 fryings)