According to the U.S. EPA Used oil is any petroleum-based or synthetic oil that has become unsuitable for its original purpose in respect whether use or handling. This due to the presence of impurities or loss of original properties. While the term "waste oil" is used to mean used oil (or oil) that is inappropriately mixed with hazardous waste, or disposed of. Nor the oil burned for energy recovery or re-refined is waste oil. The general difference between the two terms is essentially whether the used oil is disposed of, or appropriately recycled.
Oils that are off-specification typically contain: Arsenic 5 ppm, Cadmium 2 ppm, Chromium 10 ppm, Lead 100 ppm, Flash point 100°F, minimum (i.e., fp must be greater than 100°F), Total Halogens >4,000 ppm.
Waste oil can be disposed of in different ways, including 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), and 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).
For on-site burning of used oil, the 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). Waste oil furnace is a type of furnace used for heating purposes and is fueled by used oil that is free of hazardous contaminants, as described by the EPA. Waste-oil-fueled boilers can be used for various industrial purposes as well as heating.
Some examples of types of products that after use, can be labeled as used oil are: hydraulic oil, transmission oil, brake fluids, motor oil, crankcase oil, gear box oil, synthetic oil, and grades #1, 2, 3, and 4 fuel oil.
