But it has its benefits that are well worth even if it was a pain in the butt to switch back. N/A cars get crank pressure relief, Turbo cars get the benefit of not having the case pressurized and ALL of them get better octane rating and less gum up.
Turbo is another matter - that changes the intake pressure and screws up the normal function of the crankcase ventilation system, on top of whatever else it might do. I'm only concerned with NA cars that are burning oil. Assuming the crankcase ventilation system is working properly the crankcase will not be pressurized because there are two paths that will keep pressure no higher than the intake manifold. What this has to do with octane I have no idea, unless there is so much oil mist and blow by going back into the intake that it becomes a significant source of hydrocarbons inside the cylinder. The catch can should help with crud gumming up the PCV valve, but on the flip side, the PCV valve is designed to be lubricated by the oil coming out of the crankcase.
This new can design utilizes the stock OE routing, but still catches all the oil, sludge, bow-by and moisture.
Unless excessive, the oil, blow by, and moisture in the crankcase are supposed to go through the crankcase ventilation system into the intake, and back into the motor. If 99% of the exhaust gas goes out the exhaust and 1% gets by the rings, then when the 1% goes back into the motor 99% of it will go out the exhaust. Nothing builds up because, eventually, it all goes out the exhaust. If the motor is generating sludge, that is, tarry hydrocarbons, that would be bad for the PCV, but does that have anything to do with most motors that are burning a little oil?
The picture shows what looks to me like an emulsion of water and oil. Put oil, water, and a tiny bit of emulsifier (possibly from blow by gasses) in a can and shake it at high frequency, like in an engine compartment, and that is what you will get. A little oil is visible on top, either separating out of the emulsion or possible separately deposited from oil mist. The more water in the intake (humidity) the more of this stuff that will form. Common wisdom is that "oil and water don't mix", but that goes out the window when you start adding unknown other chemicals to the mix and shake the hell out of it. That goop doesn't look like sludge to me, as sludge is much darker.
Edit: After a bit of research, it turns out that emulsifiers are a normal component of motor oil, so this is exactly what one should expect to see whenever one shakes a can with car oil and a bit of water in it.
