This study presents an approach to enhance the performance of lubricating oils through the environmentally friendly synthesis of cerium oxide (CeO 2) nanoparticles using Moringa oleifera leaf extract. These biosynthesized nanoparticles were thoroughly characterized for their structural and thermal stability by utilizing X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The CeO 2 nanolubricants, prepared at various concentrations, displayed significant improvements in viscosity, stability, and thermal conductivity. Specifically, the 0.15 wt% concentration achieved the best performance, reducing viscosity to 9.79 pascal-second (Pa·s) at 80 °C while exhibiting excellent dispersion and minimal sedimentation over time. The thermal conductivity tests revealed a notable 43% increase in heat transfer efficiency at higher nanoparticle concentrations. Tribological tests conducted using a tribometer demonstrated significant improvements in the lubrication properties. The nanolubricant with a 0.15 wt% concentration of CeO 2 nanoparticles achieved the lowest friction coefficient, showing an approximate 26% reduction compared to the base oil, along with a notable decrease in wear rate. This study demonstrates the potential of biosynthesized CeO 2 nanoparticles as effective, sustainable additives in lubricating oils, providing improved thermal, rheological, and tribological properties and marking a significant step toward eco-friendly lubrication solutions.