the seal will be deformed when there is pressure, the inner diameter of the seal becomes larger and the cross-section is oval, thus sealing the tiny gap between the cartridge and the base and not leaking oil. The gasket can make the cartridge and the base fit more tightly, thus preventing oil leakage.
the initial compression in radial or axial aspect during installation gives the o-ring its own initial sealing ability. the sealing force generated by the system pressure is combined with the initial sealing force to form the total sealing force, which increases with the system pressure. O-rings show a prominent role in static sealing applications. however, in dynamic and appropriate situations, o-rings are also often used, but it is limited by the speed and pressure at the seal.