An experimental evaluation of the effect of ZnO nanoparticles on the rheological behavior of engine oil

This study investigates the effect of zinc oxide nanoparticles on rheological behavior of SAE 50 oil at different temperatures. For this purpose, nano-lubricant samples were prepared by a two-step method and those viscosities were measured by CAP2000 + viscometer. The viscosity of several nano-lubricant samples were measured at various shear rates and temperatures. Viscosity measurements at different shear rates revealed that all nano-lubricant samples had Newtonian behavior. The results showed that the maximum increase in viscosity was 12% that occurs for more concentrated samples at low temperature. The results of relative viscosity were also compared to previous theoretical and experimental works. The comparisons showed that the previous models are unable to predict the viscosity of ZnO-SAE50 nano-lubricant. Therefore, based on viscosity measurements, a new correlation as a function of ZnO volume fraction and temperature has been proposed to predict the viscosity of the nano-lubricant.