In "normal land" I would conclude that thermostat is not closing completely. Somebody out there with another oil burner to act as a control.

"New doesn't mean fixed" I say all three time. You could pull the heater wire on the thermostat and confirm if the engine is deciding it wants to new cooler and determine what the natural open temp is for the thermostat. On gas 3.0, I'm used to seeing about 90-95C which is a lot different from your numbers.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)