The antimicrobial activity of an MKF-18NT multifunctional antifriction concentrate that is the modification of one of the most common metal plating agents, an MKF-18 copper-containing additive, has been studied. It has been found that the MKF-18NT concentrate is an efficient biologically active substance exhibiting high biocidal activity against bacterial and fungal microflora. It has been shown that, being introduced into mineral and semisynthetic oils, the MKF-18NT additive inhibits the growth of moulds and thereby which promotes a decrease in microbiological corrosion. The optimum concentration of the lubricant additive MKF-18NT from the standpoint of its fungicidal action has been determined on the basis of published data and the experimental results obtained.