Evaluation of deterioration of engine oil properties in the function of mileage

The paper involve testing of various engine oils - synthetic and semi - synthetic - in terms of viscosity change at different temperatures and the degree of wear. New and used oils were compared. This is an important issue for determining the reliability of motor vehicles, anticipated repairs and maintenance. As a result of the process of exploitation, engine oils are subjected to physicochemical changes. The impact on the deterioration in the condition of the lubricating liquid have, among others high pressure, temperature, pollution or oil oxidation. Therefore, it is necessary to change the engine oil after the mileage recommended by the producer . However, these recommendations may not be adequate for the actual consumption of liquids, which is determined by the technical condition of the engine and the course of the operation process. Determining the optimal replacement time is an important issue due to the reduction of operating costs and reduction of emissions of environmentally harmful exhaust. For this purpose, the viscosity depending on the temperature of different oils with various degrees of wear, tear, and obsolescence were measured. Characteristic points were determined and a mathematical model describing these changes was created. It was noticed that the greatest changes in viscosity occur at a temperature of 0 °C to 40 °C, whereas from 40 °C the viscosity changes appear in a smaller range for all oils and the viscosity was below 100 mPa·s. Results of comparing the new and used oil was evaluation of the change of their lubricating properties. The aim of this paper was to conduct viscosity tests of selected engine oils using a rotational viscometer in order to check the degree of engine oil consumption due to the degree of exploitation.