The final target of this study is to discover the concert effect between ZnDTP and ashless FMs (polar compounds) that improve friction reducing performance together with keeping the good antiwear performance of ZnDTP. Evaluation of tribological performance and ZnDTP tribofilm formation were performed with a ball-on-disk type rolling-sliding tribometer. The tribofilm generated on the disk was analyzed by FT-IR analysis, Auger Electron Spectroscopy (AES) and Electron Probe Micro Analysis (EPMA). It was found that amino compounds showed a blocking effect, in which the ZnDTP tribofilm formation was prevented and the friction coefficient increased, whereas carboxyl compounds showed a concert effect, in which the friction coefficient was reduced with maintaining ZnDTP tribofilm formation.