A PCV system takes into account performance and emissions, but with a big emphasis on emissions. It's supposed to reduce pressure. In a perfect world, we'd like to see 0 psi in the crankcase but ...

The crankcase ventilation system for Mack’s MP8 engine shows: (1) the engine outlet for crankcase gases, (2) the separator where crankcase gas is condensed, (3) the condensed oil return to the ...

If the engine is producing blow-by gases faster than the PCV system can dispose of them, an increasing surplus becomes trapped in the crankcase, causing excess pressure and, inevitably, oil leaks.

If the engine is producing blow-by gases faster than the PCV system can dispose of them, an increasing surplus becomes trapped in the crankcase, causing excess pressure and, inevitably, oil leaks.