Waste oil is defined as any petroleum-based or synthetic oil that, through use or handling, has become unsuitable for its original purpose due to the presence of impurities or loss of original properties. The term "waste oil" means the used oil (or oil) that is inappropriately mixed with hazardous waste, or disposed of, rather than recycled (re-refined, burned for energy recovery, etc.).

• Sending the used oil off-site (some facilities are permitted to handle the used oil such as your local garages and local waste disposal facilities),
• Burning used oil as a fuel (some used oil is not regulated by burner standards, but others that are off-specification used oil can only be burned in either industrial furnaces, certain boilers, and permitted hazardous waste incinerators),
• Marketing the used oil (claims are made that the used oil is to be burned for energy recovery, it is then shipped to a used oil burner who burns the used oil in an approved industrial furnace or boiler).

Oils that are off-specification typically contain: Lead 100 ppm, Chromium 10 ppm, Arsenic 5 ppm, Cadmium 2 ppm, Flash point 100°F, minimum (i.e. flash point must be greater than 100°F), Total Halogens >4,000 ppm

Storage of waste oil
This used oil must be stored in tanks or containers, above or underground. The containers must be in good condition with no leaks, the tanks/containers must be labeled with the words “used oil”, and there must be a spill prevention plan (or a control and countermeasures plan).