You can replace the valve stem seals. After 300k miles they will be hard and brittle.
HERE is the document that tells you how to do it. Contact forum member wHunter and he should be able to get you a kit.

That looks like something a journeyman DIY mechanic could do. Is there a similar procedure for the 603 engine?

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

It sounds like turbo seals, check out the turbo, see if its wet.

If its valve steam seals usualy you will see some blue smoke on start up then it will go away.

The crankcase vent has nothing to do with the turbo, the turbo is lubed via a high pressure oil line.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

On the 116 chassis 617 turbo the CCV goes directly to the bottom of the U tube right to the turbo so it would spit any oil right there.

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-E300d '99 350k
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Sold
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Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

I'm talking about failed turbo seals, the turbo is lubed via a hard high pressure oil line. The shaft spins at like a million RPM and the seals wear out, causing high oil consumption.


CCV system has nothing to do with this.

__________________
2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200