Results are reported from laboratory studies of the influence of nitrogen-containing additives on the friction and wear of metallic pairs in diesel fuel. The elemental composition, structure, and thickness of protective films formed on friction surfaces due to the wear of moving pairs in various media are analyzed by X-ray photoelectron tomography. It is shown that the protective film is 1.5 times thicker if the diesel fuel contains a nitrogen-bearing additive rather than no additives.