In this video Melling Technical Director, George Richmond talks about flow & pressure. Oil pumps produce a flow of oil. Resistance to that flow is created by critical clearances in your engine such as main, rod and cam bearings, lifter bores and rod side clearance.

This resistance to the flow of oil is what creates oil pressure.

Most pumps have a bypass valve controlled by a spring to regulate oil pressure in your engine.
So pumps produce oil flow and regulate the pressure in your engine.

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