AbstractThe antiwear (AW) and extreme‐pressure (EP) properties of some metallic dialkyl‐ and diaryldithiophosphates (MDTP), including zinc, have been studied in different metal/metal contact conditions: four‐ball and FZG rigs.It was noted that with pure dialkyldithiophosphates of different divalent metals (Zn, Cd, Cu, Pb, Ni, Co), prepared from the same alcohol, four‐ball, EP results, expressed in terms of load‐wear index, show that the highest performances are obtained with ZnDTP, but, statistically, the higher the ionic radius of the metal, the better the performance, while EP results, expressed in terms of weld load, do not show any difference between the MDTPs. Four‐ball AW results, expressed in terms of wear scar, show that the highest performances are obtained with ZnDTPs; beyond a certain value these performances with Zn and Pb are almost independent of the concentration. For the other metallic DTPs, there is a very close relationship between performance and concentration.On the FZG gear rig, EP‐AW results, expressed in terms of failure load stage and specific wear, show that statistically, the higher the ionic radius of the metal, the better the performance. With ZnDTP four‐ball, EP results, expressed in terms of load wear index, do not depend on the chemical structure of the alcohol used for synthesised ZnDTP, but, if results are expressed in terms of weld load, better performances are obtained with ZnDTP synthesised from secondary alcohols. AW results show that the effectiveness of ZnDTP from secondary alcohols is slightly higher when the alcohols used contain less than six carbon atoms. Beyond six carbon atoms in primary or secondary alcohol molecules, performances decrease. FZG, EP‐AW results show that performance does not depend on the primary or secondary nature of the alcohols used, and that th