How is the lubrication oil in a car engine prevented from leaking out?

The main oil leakage potential is from the moving parts which run external from the engine, most of these parts are sealed using a variety of materials, rubber, plastic type materials, & cork. Non moving parts are also sealed such as rocker shaft & camshaft covers using similar materials. But one of the main reasons oil is not forced out of the engine is to have a system which allows the engine crankcase to breath and release any internal pressure build up.  more