The purpose of a pre-lubrication pump is to prime the engine’s lubrication system by circulating oil to critical moving parts before the main engine starts. This early lubrication coats surfaces such as bearings, crankshaft journals, rods, camshaft, and connecting components, so there’s oil in the passages and a film of protection as soon as cranking begins. Why this matters: when the engine is first cranked, the main oil pump hasn’t yet built up full pressure, and metal-to-metal contact can cause scuffing or wear. The pre-lubrication pump provides a low-volume, initial flow to reduce that dry-start risk, ensuring the bearings and other potential wear points are coated and protected as the main pump takes over during normal running. Other pumps serve different roles. The main oil pump provides continuous lubrication during operation by delivering oil under pressure to the system. The terms supply pump and booster pump refer to other functions in various systems and aren’t about delivering initial lubrication before startup.