Thanks for the prompt response, but I was not counting on my gauge. I work in a research lab and have an access to NIST calibrated IR sensors and platinum thermocouples. I know for a fact that when my needle moves to the right of the 90°C mark, the temperature of the coolant entering the radiator is more than 100°C.

 

silverd2, what range would be considered "normal operating temperature" and where would you take the measurement - radiator inlet? expansion tank?
Also, if outside temperature is 75 F, does your car have the need to switch the aux fan to keep the engine temp within specs in slow traffic or the belt-driven fan does the job (A/C is off, aux fan is off too)