I do wonder whether the time has come for the OEMs to fundamentally rethink what they do with engine blow-by.
As I recall, GM invented the Positive Crankcase Ventilation system in WWII. They then 'gifted' it to the world in the 1960's to get rid of the polluting draught-tubes that dumped all sorts of nasties into the atmosphere.
The simple PCV system on simple engines has served us well for decades but there are several developments that to me, seem to me to be causing the PCV system to be more of a viability than an asset. We have to move to thinner, lighter and potentially more volatile engine oils. Turbochargers and other forms of forced induction are becoming the norm rather than the exception. Piston rings are thinner and have lower tension than ever before. The power density of engines has increased greatly and at peak power run significantly hotter. We have gasolines that are more likely to contain stuff that may not burn cleanly. Finally we have GDI engines emerging where the intake system is no longer 'washed' by fresh gasoline.
The original PCV system was designed to burn blow-by gas that was predominantly contaminated with fuel. However today's PCV systems are increasingly having to deal with higher amounts of blow-by that's contaminated with both fuel AND OIL! It's the latter that causes me so much concern. Clearly it causes the OEMs concern too as evidenced by the effort they put it to separator design but these are next to useless then oil is truly in the vapour phase. Once oil gets passed the PCV all sorts of fun and games can start. Fouled inlet valves, chamber deposits, knock (I firmly believe that LSPI is caused by oil burning), ring deposits, stuck oil control rings, etc, etc.
Oil is meant to stay in the crankcase. When in the crankcase, the additives in the oil do a good job of protecting the oil from oxidation. However those same additives do nothing if the oil is set on fire! What's more, oils are designed to cope with the products of fuel combustion but NOT the far dirtier by-products of engine oil burning.
Right now, the only way of decoupling blow-by from the intake is by fitting a catch can. Whilst I can sympathise with the logic, you should not be doing this as an individual; the OEMs should be actively tackling this problem on the the behalf of everyone!
