Motor oil, engine oil, or engine lubricant is any of various substances (comprising oil enhanced with additives) which are often used for lubrication of internal combustion engines (cars, motorcycles, lawn mowers, engine-generators, and many other machines).

Oil recycling also benefits the environment: increased opportunities for consumers to recycle oil lessens the likelihood of used oil being dumped on lands and in waterways.

Recycled motor oil can be combusted as fuel, usually in plant boilers, space heaters, or industrial heating applications such as blast furnaces and cement kilns. Recycled motor oil can be distilled into diesel fuel or marine fuel in a process similar to oil re-refining but without the final hydrotreating process.