In this moment the internal combustion engines use mineral oils, semisynthetic and full synthetic oils for lubrication processes of the moving components. Exploitation interval of lubricants is close dependence of the supplied fuel, effective number of engine’s operating hours, exploitation conditions, operating regime and of the oil oxidation level. Determining the contamination coefficient is realized through weighing the available volume of oil before and after operation. Using last generation equipment there are realized experimental determinations concerning the water content through automatic coulumetric titration, density, flash point, mineral acidity, alkalinity and dielectric rigidity, of which at least four are graphically represented. It is observed that after biofuel operation the oil has accumulated more water.