medium; We have developed a gear oil with molybdenum disulfide. As the basic component, we chose PS-28 residual oil freed from medium-sulfur petroleum mixtures by solvent extraction. To improve the thermal oxidative stability, and also to increase the effectiveness of the solid additive's action, we added ester-2 (the reaction product of the esterification of pentaerythritol and the C5-C 9 fraction of fatty acids) and dioctyl sebacate (DOS), the properties of which are shown in Table i, into the oil. Dneprol, an ashless, detergent/dispersant benzylamine additive, was selected on the basis of investigations, as a stabilizer for the molybdenum disulfide dispersion. To improve the antifriction and antiwear properties, we introduced the additive ADTF into the oil. As the solid additive, we used DM-I molybdenum disulfide. We prepared the oil samples in a mixer with heating at 80~ for i h. We first dissolved the additives in the base oil and then introduced the molybdenum disulfide. An increase in the concentration of molybdenum disulfide improves the antiwear (regardless of the test temperature) and antiscoring properties of the base oil: D w decreases and I s increases (Fig. i). As the temperature rises, the effectiveness of the molybdenum disulfide increases despite the fact that the absolute value of the diameter of the wear spot at 250~ increases. The optimum concentration of molybdenum disulfide is 1.5-3% (mass). In this case, a sufficiently strong, lubricating film forms on the friction surface and molybdenum disulfide, also in sufficient amount, simultaneously enters the friction zone. We studied the TABLE i