On my 740T it took a VERY long time on a cold (this is SF bay area "cold") day for the oil temp to reach even 180F, long after the coolant thermostat was open, and it never came close to the thermostat temp. unless I was flogging it; that's why I have a 940T oil heater/cooler (oil-water heat exchanger). It still takes quite a while, but at least it gets to 120 fairly soon. Turbos like hot, but not too hot, oil.
In theory, moving parts of the engine are oil-cooled, with the oil transferring heat to the coolant, but usually the engine's under such a small amount of stress the oil needs help.
I AM running Mobil 1; maybe dino oil's different.
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