The effect of the unit load on friction and wear of metal pairs in the presence of synthetic lubricants was investigated: diester oil and oil based on polyhydric esters. The effect of these materials on the contact fatigue strength of the balls was demonstrated. Diester oil reduced the friction coefficient of steel pairs when the unit load increased from 4 to 20 MPa. The composition and structure of films of secondary structures in the surface layer of the steel sample worn in diester oil were investigated by layer-by-layer Auger spectroscopy. During interaction of friction triads, the friction zone was saturated with atomic carbon with a region of iron carbides beneath it.