Theoretically, it is. Oiling makes demoulding more convenient. Otherwise, two kinds of results are malignant: the demoulded cake is grotesque, and the other is to clean the stickiness with a bubble mold. But it is not absolutely necessary to brush oil now. For example, the better silicone baking mold, the first company, is really unique. His platinum silica gel has really come true, without brushing oil and touching it at all. Very friendly to people who bake white and reduce fat!