This study investigates the tribological effects of nano-sized metal oxides (ZrO2, CuO, Y2O3 and TiO2) in Group III type base oil containing 0.3% pour point depressant (PPD) and 5% viscosity modifier (VM) to enhance friction and wear performance. The homogenized lubricant samples with varying concentrations of oxide nanoparticles (0.1–0.5 wt%) on a linear oscillating tribometer performed static and dynamic frictional tests. Optical and confocal microscopy surface analysis evaluated the wear of the specimen, and SEM and EDX analyses characterized the wear tracks, nanoparticle distributions, and quantification. The cooperation between PPD and nanoparticles significantly improved friction and wear values; however, the worn surface suffered extensively from fatigue wear. The collaboration between VM and nanoparticles resulted in a nanoparticle-rich tribofilm on the contact surface, providing excellent wear resistance that protects the component while also favorably impacting friction reduction. This study found CuO reduced wear volume by 85% with PPD and 43% with VM at 0.5 wt%, while ZrO2 achieved 80% and 63% reductions, respectively. Y2O3 reduced wear volume by 82% with PPD, and TiO2 reduced friction by 20% with VM. These nanoparticles enhanced tribological performance at optimal concentrations, but high concentrations caused tribofilm instability, highlighting the need for precise optimization.

In this study, the design of experiments (DOE) method is used to find the optimum values of the tribological system in a 40–120 °C range with 0.1–1 wt% zirconia nanoadditives in a base oil. Significant factors were identified. The studied parameters include friction absolute integral, static friction, the wear scar diameter and the wear volume of the specimens. The measurements were carried out on a tribometer. The results were pre-estimated using statistical software; then, validation measurements were made using the estimated optimum point. The results show that the FAI value differed by 0.008, the COF value by 0.017, the WSD value by 4 μm and the WV value by 110,000 μm³. At 1 wt%, zirconia can have a positive effect at high temperatures. As temperatures increase, wear parameters decrease and friction values remain stable.