your injectors could be worn,and pissing away diesel,you need to check as they can burn a hole thru a piston.very low miles suspect they could be sticking.would not worry about diesel used in oil,I had to clean a gas motor,because screen was clogged.I fill engine up after drain oil with a gallon diesel.Ran it with the starter over 5 turns,then drain,and filled with new oil.Its a crude way to clean a engine,but it worked.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran