Oxidation and corrosion inhibiting properties of nitrogen-containing phenol oligomers in base engine oil are investigated. It is shown that in the presence of benzoguanamine and benzoguanamine oxypropylates, the basic matrix containing products of oxypropylation of phenol and monoalkyl phenols (C-8-C-12 alkyl radical) has a higher thermal stability and a lower corrosivity. The results obtained are substantiated.