Oil immersion tests of steel blocks in liquid paraffin containing a complex of lanthanide diethyldithiocarbamate and phenanthroline were carried out at various temperatures for two test durations. The friction and wear properties of protective films formed during such oil immersion tests were evaluated using a one-way reciprocating friction tester. The chemical composition and chemical state of the protective films formed during this immersion were investigated using X-ray 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.