This research focuses on the effect of nanomaterials on the physical properties of a local Iraqi lubricant oil (20W-50), which is widely used in diesel engines. The concentrations of 0.001, 0.2 and 0.5 wt% of Al2O3 NPs and CNT are dispersed in the oil with the help of a suitable surfactant using a magnetic stirrer and a sonication process. The density, surface tension, dynamic viscosity, kinematic viscosity, flash point, fire point, pour point, thermal conductivity, thermal images, wear and the coefficient of friction of the oil with and without nanomaterials are tested. The results were shown that the higher concentrations of NPs, the better properties for the engine oil. The density for Al2O3 nanooil indicates a small change at 0.001 and 0.2 wt%, and a decrease at 0.5 wt% ratio. Also, the density of CNT oil shows a slight change at 0.001and then decreasing at 0.2 and 0.5 ratios. In addition, the surface tension of both nanooils are increased. The dynamic viscosity slightly change with an addition of the NPs especially at 20°C and 30°C. Also, there is a convergence in the viscosity values between base and nanooils at 40°C and 50°C. Also, the dynamic viscosity indicates shear thickening behavior at low shear rate, while in the high shear rate the viscosity attempts to be more stable. The kinematic viscosity increases with an increased concentration of the NPs at 40°C and 100°C for both nanooils. The flash and fire point are increasing for both nanooils and Al2O3 nanooil indicates a lower pour point than that of CNT oil. CNT oil indicates higher dissipating heat friction and thermal conductivity than that of Al2O3 nanooil. Thermal images are supported by thermal conductivity and flash point behavior, while the tribology tests are compatible with viscosity behavior. A significant reduction in the coefficient of friction and wear loss is produced for both nanooils.