It very well maybe the thermostat or whatever device that's actually controlling it- just can't get wrapped around the idea that modern stuff is still using the treated spring method thats been around for 100 years now.

Not to beleaguer the point, my experience with diesel temp. is quicker during WARM UP and once underway tend to loose some of their heat. The OTR guys, that have trucks with motorized vanes, usually are closed (ambient dependent) ripping down the highway and tend to open in town/idle. Unscientific by a long shot, an observation & with some real world driving is all.

To feed off this, would anyone know if the 6.2 and the 6.7 have the same cooling system in the SD's? Did notice that the new one has a canted radiator and looks to be aluminum....