LAUSR

Abstract The viscosity behavior of 5W50 engine oil containing MWCNT and Al2O3 with the commbination ratio of 1:9 is investigated in present study. This nanofluid is prepared with various volume fractions of nanoparticles ( φ ) in the laboratory. By studying variations of viscosity at different φ , T, and shear rates ( γ ), it is found that the nanofluid has a non-Newtonian nature, which causes the γ to play a significant role in its rheological behavior. Hence, a novel correlation for viscosity as a three-variable function is obtained. Investigation of the variations of viscosity with the three variables also apparently reveals that variations of viscosity with γ at lower temperatures is much higher than its variation at higher temperatures. Thus, in higher temperatures and φ , viscosity to a great extent can be considered independent of γ . Moreover, the accuracy of the proposed correlation is examined and sensitivity of viscosity to the 10 % variation in φ , for three different γ , is analyzed. It is found that at higher temperatures and φ , viscosity is severely sensitive to small variations of φ and it blows up suddenly.