# Synergistic Effects of CuO and ZnO Nanoadditives on Friction and Wear in Automotive Base Oil +
###### Abstract
When dispersed at optimal concentrations, especially 0.1 wt% ZnO, these nanoparticles increased the lubricant's load-carrying capacity by up to 250% compared to the base fluid, primarily due to their higher hardness and the formation of a protective tribofilm on rubbing surfaces. Surface analyses confirmed that both Zn and ZnO nanoparticles were tribosintered onto steel surfaces, reducing surface roughness and preventing direct metal-to-metal contact, which led to lower friction and wear rates and improved the overall efficiency of mechanical components [19]. Researchers who have compared different oxide mixtures have found that hybrid metal oxide systems have much potential. In their research on CuO-TiO\({}_{2}\) hybrid nanofluids in gear oil, [PERSON] found that a mix of 0.3% CuO and 0.3% TiO\({}_{2}\) lowered the coefficient of friction by 19-23%. They also found that a mix of 0.1% CuO and 0.3% TiO\({}_{2}\) lowered wear by 23% and increased the load-carrying capacity by 89% compared to base oil. Their mechanical study showed that TiO\({}_{2}\) acts as nano-bearings to roll things, and CuO makes protective tribofilms. This shows how important it is to carefully optimize the ratios and distribution to get the most out of the synergistic interactions. With careful tweaking of concentration ratios and dispersion methods, these data support the idea that CuO-ZnO blends could achieve similar or even better performance through complementary mechanisms [20]. The examination of existing evidence reveals both advantages and drawbacks. Single-component nanoadditives such as CuO and ZnO yield quantifiable enhancements but have ongoing challenges: The pronounced propensity of ZnO for agglomeration reduces its efficacy, whereas the possibility for CuO to agglomerate may exacerbate abrasive wear and elevate obstruction risk. Hybrid or composite nanoparticles, combined with new synthesis techniques (e.g., sonochemical and green synthesis), mitigate specific challenges; yet, their synergistic mechanisms and long-term practical effectiveness necessitate further validation. Additional research has demonstrated that altering particle morphology and distribution enhances performance, including lubricant stability, viscosity, and high-temperature durability. Moreover, hybrid nanomaterial systems frequently surpass their single-oxide equivalents for insulation and thermal stability. The interaction between nanoparticles and prevalent lubricant additives (e.g., MoDTC, ZDDP, detergents, dispersants) substantiates the argument for synergistic approaches; however, attaining the appropriate equilibrium is precarious: for instance, an excess of CuO may elevate friction instead of diminishing it. Although the advantages of CuO and ZnO as separate nanoadditives are established, comprehensive research on the ideal ratios, underlying synergistic mechanisms, and long-term dispersion stability of CuO-ZnO mixtures in automotive base oils is limited. Research on large-scale synthesis, environmental implications, and integration with conventional lubricant formulations under actual operating circumstances is relatively restricted. This study systematically evaluates the tribological performance, mechanistic interactions, and stability of CuO-ZnO mixtures through controlled synthesis, advanced characterization, and rigorous performance testing to establish the scientific foundation for synergistic enhancement in automotive lubrication. This experimental investigation addresses these gaps by carefully assessing the tribological performance, mechanistic relationships, and stability of CuO-ZnO mixtures using controlled synthesis, improved characterization, and rigorous performance testing. The method utilizes sophisticated surface alterations and an extensive analysis of the mechanisms that dictate synergy. The primary objective is to elucidate the scientific concepts underlying CuO-ZnO synergy, facilitating the development of advanced high-performance automotive lubricants and enhancing sustainability, efficiency, and durability in mechanical systems.