The results of a study of oligomerization of phenol and some of its derivatives by reaction with propylene oxide in the presence of the nitrogen-containing modifier benzoguanamine are submitted. The structure of the synthesized oligomer is suggested. The zone of annihilation of mixtures of bacteria and fungi by adding the obtained products as additive to I-40 lube oil is determined. The bactericidal and fungicidal effectiveness of nitrogen-containing oligomers with ethanol, namely, 8-hydroxyquinoline, is compared.