In this study, the preparation and identification of Cu₂S nanoparticles were carried out using the microwave method, and the effect of irradiation time, power, and surfactant on particle size was investigated. The sample was characterized by XRD measurements, field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR), and ultraviolet-visible (UV-VIS). Also, the results of FE-SEM on nanoparticles prepared with four surfactants, EDTA, sorbitol, citric acid and PEG400 showed that nanoparticles synthesized with PEG400 surfactant have the smallest size. Then, the effect of microwave power on the size of Cu₂S nanoparticles was investigated at three powers of 700, 500 and 900 W. The FE-SEM results showed that Cu₂S nanoparticles have the smallest size at 500 W. To investigate the effect of time on the size of Cu₂S nanoparticles, the experiments were repeated at times of 3, 5 and 10 minutes, and the FE-SEM results obtained from this stage showed that after 10 minutes, Cu₂S nanoparticles have the smallest size. Also, the effects of the prepared Cu₂S nanoparticles on the thermal conductivity (K), density and viscosity of engine oil were investigated. The results obtained from this research show that the increase in electrical conductivity compared to the base oil indicates that these nanoparticles improve the heat transfer ability and operation of engine oil in harsher temperature conditions.