Abstract: 1-methyl-3-hexylimidazolium phosphate ionic liquid (Peh106) was synthesized and evaluated for steel/Al contacts in ball-on-disk tests on an Optimol SRV oscillating friction and wear tester under variable sliding frequencies and loads. The results show that the tribological properties of Peh106 were better than that of conventional ionic liquids (LB106 and LP106) and liquid paraffin (LP). Peh106 reduced the wear volume of wear scars and the mean friction coefficient. The morphologies of wear scars of Al blocks and chemical compositions of the boundary films on Al blocks were analyzed using scanning electron microscope (SEM) and X-ray photoelectron spectrometer (XPS). The SEM and XPS analysis shows that the boundary lubricant film on the worn surface of Al block prevented the direct contact of frictional pairs and improved the tribological properties of Peh106.