An additive that improves the tribotechnical characteristics of TAp-15 base oil was developed for heavy-duty friction units. The additive contains 1.35-1.6 % finely disperse high-density polyethylene, 1.55-1.75% ethyl silicate 40, and 0.085-0.095% chromium(III) acetylacetonate. A probable molecular mechanism that takes into account the synergism of the positive effect of the last two components is proposed.