Virgin and recycled engine oil differentiation-A spectroscopic study
From the results it can be concluded that the recycling processes used for purification of the sample oils are
not adequate, particularly in dealing with oxidation products
and trace metals such as Pb, Fe and Si. The presence of oxidation
products and trace metals in engine oils could primarily have a deleterious effect on equipment due to
severe erosion. However, the use of more advanced methods to remove such potential pollutants from waste oils involves higher preparation costs, making such oils uncompetitive with virgin oils.