The synergistic effect of different types of solid particles in liquid lubricants is of great interest. In this work, g-C₃N₄ nanosheets were initially prepared using a calcination method and then as-prepared, and h-BN were used as lubricating additives to the white oil. A comparison between the mixed additives and the single g-C₃N₄ or h-BN additives revealed that the base oil with the addition of g-C₃N₄ and h-BN showed the best lubricating properties. The results show a 12.3% reduction in friction coefficient, resulting in a 68.6% reduction in wear rate compared to the white oil when filled with 0.5 wt% g-C₃N₄ and h-BN (1:1 by weight). Moreover, the addition of g-C₃N₄ and h-BN improves the high-temperature lubrication properties of the white oil. However, the friction coefficient and wear rate increase with increasing oil temperature. The large contact area between g-C₃N₄ and its sliding counterpart and the strong adhesive force between h-BN and its sliding counterpart improve the film formation efficiency, leading to enhanced tribological properties under oil lubrication conditions.