Abstract <p>Based on the concepts of physicochemical mechanics of contact interaction, a materials-science analysis of the tribological efficiency of a number of synthetic lubricant compositions containing a surface-active additive, lithium 12-hydroxystearate, was carried out. Tests of the “CuAl5 bronze–С45 steel” friction pair were carried out on an MT-8 reversible sliding friction machine under conditions corresponding to the operating modes of heavily loaded friction units. The role of the lubricating medium was revealed using criterial approaches based on an experimentally obtained set of macroscopic integral criteria (phenomenological indicators of friction and wear) and microscopic (microstructural) criteria (physical broadening of X-ray lines, crystal lattice period, elemental composition of the surface layer of the material of the contact deformation zone) determined using modern metallophysical research methods. For the first time, it has been experimentally proven that the use of dispersion-lubricating media containing surfactants in tribocouplings promotes the formation of a wear-resistant structure in the antifriction material aluminum bronze.</p>