The present investigation aims to experimentally examine the effects of shear rate, temperature, and solid concentration of nanoparticles on the rheological properties of TiO2-MWCNT (80%-20%)/oil (5 W50) nanofluid. The rheological behavior of the nanofluid, whether it is a Newtonian or non-Newtonian fluid, has been studied in different temperatures, shear rates, and solid concentrations. It is found that the nanofluid behaves as a Newtonian fluid under the conditions of the present study. In addition, the increasing trend in the dynamic viscosity of the nanofluid has been observed as the solid concentration increases. The maximum increase has been observed at the solid concentration and temperature of 2% and 50 degrees C, respectively, by 42%. Moreover, employing the experimental results, a new correlation for estimating the dynamic viscosity of the nanofluid in terms of temperature and solid concentrations has been proposed with the accuracy of 4%. (C) 2019 Elsevier B.V. All rights reserved.