Used oils are counted among hazardous waste materials group by Polish environmental regulations. The resulting hazard to human life or health and an environmental hazard are fully justified if we analyze the chemical composition of used motor oil, for example, taking into consideration the origin of its components, the physical and chemical changes it undergoes when in use and possible contamination of the used oil when collected and stored. As a result of engine fuel combustion and especially the engine petrol combustion, the process of hydrocarbon pyrolisis occurs, as one of by-processes, which results in generation of polycyclic (polynuclear) aromatic hydrocarbons, including benzo(a)pyrene to which, according to biological and medical research is, carcinogenic properties are attributed.

The changes occur not only in the hydrocarbon part of lubricating oil. First of all the additives undergo changes and the changes result in a transfer to a different chemical and physical structure. Generally speaking, the changes lead to destruction of molecules and transfer to simpler substances. Calcium, magnesium and barium carbonates appear as well as sulphides, tio-phosphates and oxides of metals. Besides, some more complex substances are generated which are the result of chemical effect of inorganic substances on the products of hydrocarbons destruction. The products of thermal and mechanical destruction of polymers are present as well. When we supplement the foregoing with the metals abraded from mechanical parts of engines, it is easy to show that a substantial part of elements from the Mendeleev’s table in different physical and chemical configurations is involved.

The polycyclic aromatic hydrocarbons, some products of the additives reactions (e.g.: calcium sulphonates, zinc di-tio-phosphates, succinite-imino disperging agents, sulphurated phenolates, phenoles with sterical hindrance) and heavy metals (Pb, Zn, Cu, Ni, Cd, Fe, Cr, Mn) show harmful effect on biosphere and especially on the human body, which demands that used lubricating oils be collected and disposed of/managed in a controlled way with the least possible detrimental effect on the natural environment.

• used oils are an alternative source of base oil supply
• energy consumption per 1 kg of base oil from regeneration accounts for less than 1/3 of the energy necessary to produce 1 kg of virgin base oil
• regeneration contributes to conservation of non-renewable energy resources