APPROXIMATE TEST OF THE THERMAL DEGRADATION OF ENGINE OIL

Engine oils are one of the most stressed operating fluids of combustion engines. European manufacturers of combustion engines are creating degradation models of engine oils taking into account the operational conditions of each of vehicle. The engine oil is checked and changed on the base of these models. For stationary working gas engines of cogeneration units, these models are not fully suitable. This kind of combustion engines has very high requirements on the quality of engine oils, especially on the thermo-oxidative stability. Modern oils with high portion of additives are commonly used. In this case, tribodiagnostic does not serve as predictive utility, but serves as confirmation of properly chosen service period of engine oil. Experiment was set to prove the possibility of evaluation of thermo-oxidative degradation of synthetic, hydrocracked and mineral oils. The change of colour, caused due to high temperature and presence of air, was chosen as evaluation criteria. The aim of article was to set time course of colour changes. This paper presents results for synthetic, hydrocracked and mineral oils.