Optimizing the factors affecting the quality condition of 4WD tractors' engine oil using the hybrid RSM-GRA method.

Oil condition monitoring is vital for enhancing engine performance, reducing fuel consumption, and preventing wear and tear on engine parts. Tractors, like other agricultural machines, are operated in dusty or muddy and polluted environments of the farmland, which strongly affects the engine oil quality. To prevent damage to the tractor engine, assist in preventive maintenance planning, reduce unexpected stoppages and excessive repair costs, and increasing the availability and reliability of agricultural tractors, this study aimed to find the precise time of a 4WD tractor's engine oil change using RSM-GRA optimization hybrid method to determine and optimize oil change intervals in infant mortality, useful, and wear-out lives of tractors. The effect of operating hours and tractor age on the quality features of engine oil showed that all wear debris increases when tractor age and operating hours increase. However, the impact of tractor age was greater than operating hours. Overall, operating hours of 93.6 h are suggested for oil change intervals of tractors in infant mortality life, which resulted in a Fe of 0.076, Cu of 0.96, Si of 0.52, B of 0.01, Zn and P of 0.014, Ca of 0.3, Mn of 0.0072, PQ of 0.002, and the rest of the metals are zero. Moreover, operating hours of 53.22 h and 35.5 h are the optimal conditions for oil change intervals of tractors in useful life and wear-out life, respectively. As the tractor's age increases, the oil change intervals become shorter. As a result, it can be said that the tractor's age and the oil change intervals are closely related, and as the tractor wears out, the oil change interval is sometimes reduced by half.