The friction reduction and antiwear properties of a range of organo-chlorine compounds as oil additives in mineral oil were assessed using a Timken tester with a SAE52100 steel ring sliding against an A12024 block. X-ray photoelectron spectrometry (XPS) and microscopic infrared reflectance were employed to examine the boundary film formed on the surface of the Al block. The results reveal that unsaturated chlorides with electron-defect p-π conjugated system are more effective to reduce both friction and wear of A12024 block, because they are easy to adsorb on the rubbed surfaces and to form aluminum chloride and friction polymer. The lubricating mechanism was forming effective boundary films.