Motor Oil



Used mineral-based crankcase oil is the brown-to-black, oily liquid removed from the engine of a motor vehicle when the oil is changed. It is similar to unused oil except it contains additional chemicals from it's use as an engine lubricant.

The chemicals in oil include hydrocarbons, which are distilled from crude oil, and various additives that improve the oil's performance. Used oil also contains chemicals formed when the oil is exposed to high temperatures and pressures inside an engine. It also contains some metals from engine parts and small amounts of gasoline, antifreeze, and chemicals that come from gasoline when it burns inside the engine.

The chemicals found in used mineral-based crankcase oil vary depending on the brand and type of oil, whether gasoline or diesel fuel was used, the mechanical condition of the engine that the oil came from, and the amount of use between oil changes. Used oil is not naturally found in the environment.

Motor Oil

Bubbly Motor Oil Image: Wikimedia Commons

Fate & Transport

Used mineral-based crankcase oil enters the air through the exhaust system during engine use. It may enter water or soil when disposed of improperly. The hydrocarbon components of the oil generally stick to the soil surface. Some hydrocarbons evaporate into the air very quickly, and others evaporate more slowly. Hydrocarbon components of the oil that enter surface water bind to small particles in the water and eventually settle to the bottom. Hydrocarbons from used mineral-based crankcase oil may build up in shellfish or other organisms. Some metals in used mineral-based crankcase oil dissolve in water and move through the soil easily and may be found in surface water and groundwater.

Exposure Pathways

When you change the engine oil in your car

Breathing a small amount of the chemicals from the oil in exhaust fumes or from burning the oil as heating fuel

Touching contaminated soil or drinking contaminated water

Health Effects

The health effects of used mineral-based crankcase oil vary depending on the brand and type of oil used and the characteristics of the engine it came from. Mechanics and other auto workers who are exposed to used mineral-based crankcase oil from a large number of cars have experienced skin rashes, blood effects (anemia), and headaches and tremors. However, these workers are also exposed to other chemicals, which may have caused these health effects.

Volunteers who breathed mists of used mineral-based crankcase oil for a few minutes had slightly irritated noses, throats, and eyes. Animals that ate large amounts of this oil developed diarrhea. Thus, people who swallow used mineral-based crankcase oil may also have diarrhea. Some cows that ate used oil containing metals such as molybdenum and lead in contaminated pastures experienced anemia and tremors. Some of the cows died. We do not know if exposure to used mineral-based crankcase oil affects the reproductive ability of men or women or whether it causes birth defects.

Long-term exposure (365 days or longer) of the skin to used mineral-based crankcase oil causes skin cancer in mice. PAHs in the oil have been identified as the cancer-causing agents because some PAHs are known to cause cancer and because the carcinogenicity of various batches of the used oil increased with increasing amounts of PAHs in the oil. The Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified used mineral-based crankcase oil with regard to its carcinogenicity in people.

Information excerpted from:

Toxicological Profile for Used Mineral-Based Crankcase Oil 1996 Update

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services