The peculiarity of the mutual influence of aminophosphate antiwear additives and extreme pressure additives containing polysulfide groups on the degree and nature of wear and scuffing of friction surfaces is established. It is shown that it is impossible to obtain a high level of antiwear and extreme pressure properties while using these additives together to produce gear oil from recycled oils. The proposed solution of the problem is to introduce an additional additive of moderate activity. By the methods of scanning electron microscopy and energy dispersive x-ray spectral microanalysis, the presence of phosphorus on metal surface at loads close to the welding load was revealed, and the absence of phosphorus on the metal surface at moderate loads. It is suggested that at high loads, due to the high activity of aminophosphates to the surface of the metal, there is a competing formation of a phosphate film, which prevents the formation of a protective sulfur-containing layer due to an extreme pressure additive.