How does used oil damage the environment?

Once lubricating oil is drained from industries, engines, gearboxes, hydraulic systems, turbines and air compressors:

  • the oil is contaminated with wear debris
  • the lubricating base oil has deteriorated and degraded to acids
  • the additives have decomposed into other chemical species
  • process fluids, degreasers and solvents have mixed into the used oil.

Used oil contains wear metals such as iron, tin and copper as well as lead from leaded petrol used by motorists. Zinc arises from the additive packages in lube oils.

Harmful Affect of Used Oil on Environment


Many organic molecules arise from the breakdown of additives and base oils. The molecule potentially the most harmful is the polycyclic aromatic hydrocarbon (PAH) such as benz(a)pyrene and chrysene.

Petrol engines generate the most PAH molecules per 1000km, with diesel engines below that and 2 stroke engines generating the least amount of PAH.

Did you know?

A release of used oil to the environment, whether by accident or otherwise, threatens ground and surface waters with oil contamination there by endangering drinking water supply and aquatic organisms.

Used oil can damage the environment in several different ways:

  • Spilled oil tends to accumulate in the environment, causing soil and water pollution. Oil decomposes very slowly. It reduces the oxygen supply to the micro-organisms that break the oil down into non-hazardous compounds.
  • Toxic gases and harmful metallic dust particles are produced by the ordinary combustion of used oil. The high concentration of metal ions, lead, zinc, chromium and copper in used oil can be toxic to ecological systems and to human health if they are emitted from the exhaust stack of uncontrolled burners and furnaces.
  • Some of the additives used in lubricants can contaminate the environment. E.g. zinc dialkyl dithiophosphates, molybdenum disulphide, and other organo-metallic compounds.
  • Certain compounds in used oil - eg poly-aromatic hydrocarbons (PAH) - can be very dangerous to one's health. Some are carcinogenic and mutagenic. The PAH content of engine oil increases with operating time, because the PAH formed during combustion in petrol engines accumulates in the oil.
  • Lubricating oil is transformed by the high temperatures and stress of an engine's operation. This results in oxidation, nitration, cracking of polymers and decomposition of organ- metallic compounds
  • Other contaminants also accumulate in oil during use - fuel, antifreeze/coolant, water, wear metals, metal oxides and combustion products.

As it is already mentioned above that if used oil is disposed in irresponsible manner it may cause great danger to the human resources like water supply. The environmental effects of used oil can be categorized as follows.

  • Human health effects of used oil
  • Effects on Wetlands and Wildlife
  • Effects of Burning Waste oil
  • Effects on Marine and Fresh water organisms
  • Effects of using waste oil as dust control agent

Useful Links

Environmental impact of the petroleum industry
Environmental impact of the oil shale industry

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