Abstract: Two kinds of additives, namely, the heavy extreme pressure gear oil additive and polymerizable dimer acid/sorbitan additive were selected to formulate various mineral oil-based lubricants. The effect of the additives on the load-carrying capacity of the base stock and the anti-fatigue ability was investigated based on fatigue testing and seizure testing. The worn surfaces were observed with a scanning electron microscope. As the results, the polymerizable additive contributes to increase the anti-fatigue ability greatly, while the extreme pressure additive leads to decrease of the anti-fatigue ability. Optimized comprehensive properties can be reached by proper formulation of the lubricating oil containing the two kinds of additives. This is attributed to the synergistic effect of the two kings of additives in the mineral oil.