How to Clean Oil from an Oven? Oil and grease are prevalent in an oven because of cooking, baking, and grilling. The heat from the processes melts the fat, which drops on the ovens' surface and microwave ovens. These oils and greases make your oven look untidy and even give you a hard time using it. This is why it is always vital to clean oil out of an oven, especially after each process. In case you are uncertain about the right method to remove it, you will be happy to learn that several practical and straightforward tips can help.