That’s an interesting thought. The valve cover has some internal baffling inside. I’m not sure what’s under the glued in plate running a long the top. I guess it’s supposed to stop splashing.

I think my car is getting a lot of oil from worn valve guides combined with old valve stem seals. I bet it works like a really good atomizer in there during the exhaust stroke when the exhaust valve is open and the turbo is putting a bit of back pressure on the exhaust. I have some seals on the shelf to do the job. Just waiting for the valve adjustment interval.

It can only help. I’d probably look at all possible remedies before cutting a hole in my valve cover.

My separator has been working well on both my cars. I collect a tablespoon full of oil every two months with light use (300 miles a month). I figure it’s better in the cup than on my rings.

On my 300SD there is a stock cyclonic separator that I use in series with the BMW N54 style separator. The drawback of this is more backpressure. Two crank case vents would definitely drop the pressure but I haven’t had any issues yet. My engine remains well sealed.

ETA - on both of my cars I had leaking seals. Yes, it has to do with crank case pressure but it also had much to do with 40 yo hardened gaskets. I had leaking turbo drain seals/gasket, oil Pan, oil drain plug, vacuum pump gasket, valve cover gasket, breather drain seal, U tube gasket, crank case vent elbows, injector pump gasket, oil filter block gasket, main seal, oil cap gasket and more weeping. Replacing these stopped the oil leaks. Theyve withstood the addition of the extra separator can so I must admit the leaks had as much to do with old rubber as they did blow by.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles