yes, high blowby would increase the oil pressure. when i plugged the vent hose on my valve cover, oil started running out of the top of the dipstick tube.

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1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350