Nanoparticles can be added as anti-friction and anti-wear additives to lubricating oil to achieve better lubrication performance. In this study, we demonstrate that the mixing procedure of BN nanoparticles and oleic acid (OA) influences the lubricant performance of PAO8. Lower friction and wear can be realized when OA and BN nanoparticles are mixed simultaneously in PAO8 than those with pre-mixed BN nanoparticles and OA. The tribological performance of the prepared lubricant was ascribed to the synergistic effect of the migration of well -dispersed BN nanoparticles and the adsorption of free OA on the metal surface. These results suggest that attention should be paid to the potential effect of the mixing procedure of additives, which might affect the performance of lubricants.