While driving at highway speeds the temp gauge will climb way too high for my comfort. But slowing down to stop & go traffic, it cools down nicely. Recently on the Interstate, the car was running hot and we came to a traffic jam where we went from 75 to about 5mph. The car cooled right down.
It would seem to me that the car would benefit from the air flow at speed with the outside temperature is under 70 Farenheit. The coolant is full, the radiator is clear, the fans work. It's an '89 325i converted from an automatic, to a five-speed.