In your example I would think the aircon would be on all the time keeping the temperature down in the car. It's when outside temperatures are cooler, say in the range 12 to 20, that I find the car doesn't maintain a constant cabin temp. I've put this down to the car deciding that the compressor doesn't need to be run at all times in Auto even when the SC button is on. My car is much better now that I've switched Auto AC and Efficient Ventilation off. I think these settings stop the car from intelligently switching off the AC or running the fan at a lower speed. I want climate control to control the climate in my car as best as it can, I don't want climate control to save 0.5mpg or whatever it does save.