Oil immersion tests of steel blocks in liquid paraffin containing a complex of lanthanide diethyldithiocarbamate and phenanthroline were carried out ata various temperatures for two test durations. The friction tester. The chemical composition and chemical state of the protective films forme during this immersion were investigated using Xray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The results of the friction and wear tests indicated that the protective films exhibited good antiwear and reduction friction properties. It was also found that the higher immersion temperature and longer immersion duration correspond to the longer the antiwear lifetime of the protective film. The results of the XPS and AES analyses indicate that the film formed during the oil immersion tests might contain lanthanum oxide, sulfide and organic nitrogen compounds.