Abrasive wear in lubricated contact dominates the performance and lifespan of tribological systems in many engineering fields, including two-body and three-body abrasion, which are classified based on the difference in kinematics. In the present study, bearing steel (100Cr6) pins and discs in a flat-on-flat contact, were utilized in a test series with 5 μm and 13 μm Al2O3-based slurries as interfacial media to shed light on the acting mechanisms. It was found that the speed-induced hydrodynamic effects only exist when using 5 μm slurry, which can lead to a maximum of around 30% increase in film thickness and decrease the friction by around 60%. A transition from two-body abrasion to three-body abrasion and a change in wear mechanism from microcutting and microploughing to fatigue wear were also observed due to the hydrodynamic effects. Surprisingly, the total wear of pin and disc did not vary much, but the wear distribution over pin and disc was observed to change significantly. The relationship between wear mechanism and wear in this tribological system will be discussed, and this may reveal the importance of considering the global amount of wear in the tribological system.