<p>This study evaluates the performance enhancement of SAE 0W40 synthetic lubricant infused with surface-activated lanthanum oxide (La₂O₃) nanoparticles. Nanolubricants were synthesized via wet ball milling and prepared in concentrations ranging from 0.1 to 0.5 wt%, ensuring uniform dispersion and stability. Key physicochemical tests, including acid value, flash and fire point, and copper strip corrosion, confirmed chemical compatibility. Thermal and bond analyses, along with dispersion stability tests, validated nanoparticle integration. Tribological behaviour was assessed using a Four-Ball Tester. Results revealed a 64% increase in wear scar diameter and a 30% improvement in viscosity with 0.3 wt% La₂O₃ addition. The enhancements are attributed to improved film strength and thermal resilience. This study confirms the potential of La₂O₃-based nanolubricants to improve engine efficiency and durability in heavy automotive applications.</p> Graphical Abstract <p></p>