For a good while I've suspected that the half full argument is caused by a slow leak from the turbo drain tube where it hits the oil pan.

In my engine that I just installed in my SD, the oil was visible in the tube's attachment hole when the engine was sitting level in the garage, and at less than full on the dip stick.

I'm guessing that a seal in less than perfect shape, combined with a higher oil level would promote the leaking of oil, down to wherever it balanced out. The half-full mark, possibly?

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...