Fuel oil is a general term for a number of burnable liquids made from crude oil.
No. 4 is a diesel fuel for boats. All fuel oil mixtures have similar chemical and physical properties. Fuel oils are used to run many types of engines, lamps and heaters. Sometimes small amounts of fuel oil are stored in portable containers for use in space heaters, to clean metal parts, or used in camp stoves or lanterns. Most fuel oil entering the environment comes from spills or leaking storage tanks.