This study investigated the Al2O3-MWCNT presence efficacy on the thermal conductivity of the engine oil (10 W40) base fluid. Owing to the dependency of thermal conductivity on temperature and number of nanoparticles, the experimental measurements were conducted at 25-65 degrees C and volume fraction of 0.05, 0.1, 0.25, 0.5 and 1 vol %. Also, zeta potential test was performed at two different times to verify the long-term stability. Based on experiment results, at constant temperature gradient, the oil's ability to conduct heat at 65 degrees C is about 4.4% lower than that of 25 degrees C. But the addition of nanoparticles of Al2O3-MWCNT by 1 vol% into the oil augmented the heat transfer potential by 9.62%. It was found that the positive effects of adding nanoparticles of MWCNT-Al2O3 to engine oil (10 W40) on thermal conductivity enhancement were amplified at higher temperatures. Due to the incorporation of MWCNT-Al2O3 into oil, thermal conductivity enhanced up to 30.53%. Finally, through approving a regression-based correlation, Al2O3-MWCNT/engine oil (10 W40) thermal conductivity was predicted and applying analysis of variance, the thermal conductivity dependency to volume fraction and temperature were examined. (C) 2020 Elsevier B.V. All rights reserved.