Bob, I think you have the real answer here. I agree that my experience is that the engines use more oil if kept topped off. I guarantee that if you over fill the thing it will use a bunch.

I attribute the extra consumption to a larger quantity of oil vapors in the crankcase breather system which is carried into the intake as PCV.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician