Preferably, use vegetable frying oil, such as peanut oil, canola oil, corn oil, or sunflower oil. Oils with a high content of saturated fatty acids are less convenient, even if they are heat resistant. If the oil becomes frothy, it is time to change it. 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, typically after about 10 fryings.