The oil used to make fried skewers is usually changed once every two to three days, mainly when the oil is black. Unlike domestic oil, shortening or soybean oil is usually used in the street. If the amount is not large, Citi shortening can be used for 4-5 days, and it will not stink, but the oil will turn black. Under normal circumstances, it needs to be changed after several times of frying, and it is impossible to use it every day. The oil is discolored, let it cool, find a thick napkin, put down the colander and filter the oil once, and the oil will become clear.