Визначення впливу добавок соєвого метилового ефіру до товарних дизельних палив на терміни заміни оливи в дизельному двигуні 1,5 Renault моделі K9K

This study explores viscosity-temperature characteristics of Castrol GTX RN-Spec 5W-30 engine oil and its oxidation resistance. The task addressed investigates the effect of adding SME to diesel fuels on the timing of oil changes in the engine. The results showed that the maximum service life of Castrol GTX RN-Spec 5W-30 oil under specified conditions is 12 thousand km when operating on commercial diesel fuel. In the case of using mixtures of diesel fuel and 10, 20, and 50 vol. % SME, the maximum service life of cars before oil replacement according to viscosity-temperature characteristics is reduced from 9 to 6 thousand km, respectively. The total base number (TBN) indicator of all experimental samples of engine oils reaches a critical value after a run of 9 thousand km. In general, the use of fuel mixtures with biodiesel based on soybean methyl ether in an amount of up to 50 vol. % does not require a significant reduction in the oil replacement period according to the TBN indicator. The deterioration in the viscosity-temperature characteristics of Castrol GTX RN-Spec 5W-30 engine oil is explained by the fact that biodiesel fuel based on soybean methyl ether has a lower heat of combustion. The fuel mixtures do not have time to completely burn in the engine cylinders and, being washed away with the oil into the sump, partially dilute it. The accumulation of biodiesel fuel in engine oil also contributes to a decrease in the alkaline number of Castrol GTX RN-Spec 5W-30 engine oil and accelerates its oxidation process. The findings made it possible to move from general assumptions to specific regulations – reducing oil change intervals by 20–50% or introducing specialized engine oils. The results of this work could be used in the field of car service to adjust the mileage limits before oil change when operating cars on biodiesel fuel