Small- and large-sized crystalline ZIF-71 was synthesized using different strategies and has average diameters of approximately 450 nm, and 1–2 μm. Large-sized ZIF-71 particles with good crystallinity were prepared by a solvothermal synthesis method and small-sized ZIF-71 particles were prepared upon the addition of an acidic additive (formic acid) at room temperature. The two different sizes of particles were used as oil additives in liquid paraffin, and investigated using four-ball tribotesters. The results show that the small-sized particles can improve the anti-wear properties and load-carrying abilities of the base oil. The large-sized particles exhibit good load-carrying capacity. Wear surfaces were analysed by using scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and Zygo Zegage 3D optical profiler after the wear tests.