I'm not sure if this is applicable with diesel Benz's, however I read about it happening with VW TDis and experienced it myself. At higher RPMs, the intake suction actually draws oil thru the PCV. In fact, I've heard that in extreme cases (semis) so much oil is burned that it causes the vehicle to accelerate, thus drawing in more oil... until all the oil is burned up.
Please correct me if I'm completely wrong, here.