Used oil recycling is a procedure that involves reprocessing used motor oil so that it can be used again. Motor oil can be recycled indefinitely because the lubricant does not wear out. Recycled oil is cleaned of contaminants such as dirt, water, used additives, and fuel. Used oil may also contain toxic substances such as lead, benzene, zinc, and cadmium.

Recycling saves oil and helps the environment. According to the United States Environmental Protection Agency (EPA), 2.5 qt (2.4 l) of rerefined oil can be processed from 1 gal (3.8 l) of used oil. If not recycled, the gallon of lubricant from an oil change can ruin 1 million gal (3.8 million l) of fresh water, representing the annual water supply for 50 people. One pint (0.5 l) of used oil can create an approximately 1 acre (0.4 ha) oil slick on the surface of water, according to the California Integrated Waste Management Board...