Vegetable oil based lubricants attract much attention nowadays due to their excellent boundary lubrication performance and biodegradability. Coconut oil is a vegetable oil with excellent lubricating properties which provides low friction coefficient and better oxidation stability. The purpose of this study is to investigate the performance of coconut oil based new hybrid CeO2/CuO nano-lubricant with various ratios of CeO2/CuO viz. 25/75, 50/50, and 75/25 at different concentrations (0.1, 0.25, 0.5, and 1.0 wt%). The rheological, thermal, thermo-gravimetric, and tribological evaluations were conducted for hybrid nano-lubricants and the results were compared with those of base oil (coconut oil) and nano-lubricants containing CeO2 and CuO nano-particles individually. A reduction of 15.7% in average friction coefficient and 23.4% in wear scar diameter was observed with the use of 0.25 wt% CeO2/CuO: 50/50 hybrid. Oil degradation studies and worn surface analyses after engine test were also done. The results showed that the surface enhancement is evidenced with the use of hybrid nano-lubricant.
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