The homogeneous and substantial dispersion of nanoparticles into base fluids is vital since the final properties of any nanolubricant are estimated by their quality of stability. This paper addresses the effect of NiO nanoparticles dispersion into SN500 lubricant oil and its nonisothermal thermo stability. The dispersion of NiO nanoparticles is achieved by ultrasonication method. The thermo stability is estimated by Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The result shows that the thermo stability of base fluid enhances up to 0.3 wt.% particle concentration then it decreases due to agglomeration of dispersed nanoparticles. The findings recommend that 0.1 wt.% and 0.3 wt.% of NiO-nanolubricant can be used for the temperature-dependent applications up to 200∘C.