Abstract: The effect of anti-wear agents of trialkyl phosphorodithioate (P1) and trialkylphenyl phosphorothionate (P2) on anti-micropitting for gear oil was tested by analysis of the change rate of track width, CLA curve and surface topography of the roller using MPR test machine. The result showed that the MPR test machine has a good distinction to the anti-micropitting for gear oil. Compared with sample P1, the change rate of the track width of P2 is small; fewer pits on the surface of roller are found and are relatively shallow; the CLA curve is relatively steady and smooth. These results showed that P2 has better anti-micropitting ability and could lower the occurrence of micropitting for gear oil.

Key words: anti-micropitting, S-P type agent, gear oil