The friction and wear properties of the DLC coatings were evaluated while being lubricated with pure PAG, PAG containing PN and ZDDP using reciprocating ball-on-disk sliding UMT tester, respectively. The morphologies of the worn surfaces of the DLC coatings were observed using a scanning electron microscope (SEM). The results indicated that the DLC coatings exhibited better tribological properties under the lubrication of PAG containing PN or ZDDP than that of pure PAG. In addition, PN and ZDDP as additives show different tribological properties. The former offers better anti-wear ability, the latter offers better friction-reducing properties.