if the engine runs rich for excessive time, you essentially wear down the cylinders as the fuel washes the oil out.

It also doesnt allow the PCV system to work correctly as the oil never gets hot.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I doubt it is running that rich, just that some computer type thing might be treating it as not fully warmed up. I wonder what the oil temp gets to. You there may be a fear that water doesn't boil off.