I'm a little late to this discussion but I wanted to indicate what I have experienced in my 2018 Hatch sport 6 MSP. I have a Scan Gauge which provides coolant temp in parameter CT1, and the return coolant temp in parameter CT2. I have driven the car over 65,000 miles and noted that the coolant temp is almost always 170-180 deg f. It goes to the higher 180 temp when driving in positive boost. It appears the thermostat opens at 170 deg f. The CT2 temp shows how efficient the radiator is as it displays the return coolant temp after being cooled by the radiator.
So this week, I decided to take the climate control AC to Off since the outside temp was below 50 deg f. Much to my surprise, the coolant temp was seen at 205 and the return coolant was also at 200 deg f. I checked under the hood and noted that the radiator fan was not running. Once I switched the AC back on, the radiator fan immediately started running and the engine temperature immediately began dropping and the return coolatnt temp also dropped dramatically.
So it appears that when the climate control is in auto or the AC is switched on, the radiator fan will operate and the running engine temp will operate in the 170-180 deg f range. I have been driving the car for 2 years now and just noted this anamoly. So now I wonder when the fan will turn on since it cannot cool itself below the return coolant temperature. I assume nominal operation is 170 -180 deg f.
Anyone have an answer?