Synthetic oil is oil consisting of chemical compouns which were not originally present in crude oil (petroleum), but were artificially made (synthesized) from other compounds. Synthetic oil could be made to be a substitute for petroleum, or specially made to be a substitute for a lubricant oil, such as conventional (or mineral) motor oil refined from petroleum. When a synthetic oil or synthetic fuel is made as a substitute for petroleum, it is generally produced because of a shortage of petroleum or because petroleum is too expensive. When synthetic oil is made as a substitute for lubricant refined from petroleum, it is generally to provide superior mechanical and chemical properties than those found in traditional mineral oils.