<p>Marine diesel engines operate under extreme conditions characterized by high temperatures and heavy loads, leading to significant friction and wear-related losses. The incorporation of lubricant additives has proven effective in enhancing the anti-friction and anti-wear properties of base oils, with certain additives even demonstrating self-healing capabilities. In this study, calcium borate (CB)/graphene (Gr) composite lubricant additives (1^# lubricant additive) were synthesized through plasma-assisted ball milling, using Gr and CB as primary materials and oleic acid as a surface modifier. To further investigate the synthesis process, a second set of additives (2^# lubricant additive) was prepared using expanded graphite in place of Gr under the same conditions. The microstructure and surface chemistry of both additive types were characterized through scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and x-ray diffraction (XRD). Tribological performance was evaluated at varying temperatures using a reciprocating friction and wear tester. The results indicate that plasma-assisted ball milling effectively exfoliates expanded graphite into Gr while simultaneously facilitating surface modification. Furthermore, the synergistic interaction between CB and Gr, as well as the formation of a protective tribofilm on the contact surface, results in significantly enhanced friction-reducing and wear-resistant properties.</p>