In this paper, the copper oxide/aluminium oxide (CuO/Al2O3) nanocomposites were prepared by a non-hydrolytic sol method. It was found that the mean particle size of CuO/Al2O3 nanocomposites were about 89 nm with a uniform distribution by the particle size analysis. The prepared CuO/Al2O3 nanocomposites can be dispersed in lubricating oil homogenously for several weeks. The reason is that the grafted polymers are introduced by non-hydrolytic sol method. The formation of covalent bands was identified by Fourier Transform infrared spectrum. Under an optimized concentration of 0.1 wt%, the averaged coefficient of friction (COF) was reduced by 38.6%, when the CuO/Al2O3 nanocomposites sol was used as the lubricating oil additives.