Originally Posted by wemay
...Well, that's why i mentioned a variation of a CCan that doesn't require continuous maintenance. But they haven't...
They do though. Look at Mazda SkyActiv engine, there's substantial catch can built right in. GM has variation of baffled separator in the valve cover, at least in 8 cyl engines. GM actually had to re-design the valve cover for the previous-gen V8s because of excessive blow-by ending in intake.
Many manufacturers do include separators, but to make the whole assembly compact and maintenance-free they have to drain the condensate back into the sump. This makes the catch can a part of the engine. And it is not very effective(hello GM), partially because of the heat. This is why external cans collect at least something, the stuff left behind by OEM separator. Not all of it, indeed, but evidently it helps.
Intake in my Tahoe is relatively dry for the last 50k km after it got the can. When I picked the truck up it was a mess there, at 50k km. The 5.3L engine is known for its oil-in-intake problems.