What's the purpose of this button on my E90 M3?

Hi all, first time posting here (first time posting on any forum i believe )
Anyway, i've had this car for a long time, but never figured out the purpose for this particular button. This is also my first bmw, so please don't laugh too loud if my question is really dumb
I know what the button does (cooler air if roll towards blue, warmer air if roll towards red), but why? If all I want to do is adjusting temperature, why not just turn the knob and adjust the temperature setting?
i searched thru the manual, but don't think that button is even listed

This is directly from the E92 manual…

Knurled wheel for more or less cool air from the vents for the upper body area.

So if you have the automatic system set and it is heating the interior, you can turn the wheel and have relatively cooler air be directed to your face or upper areas if that is more comfortable. That being said I usually don’t mess with it.

Originally Posted by edge9

This is directly from the E92 manual…

Knurled wheel for more or less cool air from the vents for the upper body area.

So if you have the automatic system set and it is heating the interior, you can turn the wheel and have relatively cooler air be directed to your face or upper areas if that is more comfortable. That being said I usually don’t mess with it.

Correct...The temp setting is for overall setting, the mix dial controls the air you get to your face...works well.

OP, welcome to the fest!

I can tell you that the same switch goes back 30 years, long before auto climate.

I remember from the owners manual of my E36 about 20 years ago it stated the reason for having this was so that you could blow cool air to the face to help keep you more alert, without making the ambient temp too cool for everyone else. It works very well at that.

I use this feature all the time on my M3 (and all my past BMWs) but really miss it when driving my wife's Audi that doesn't have it.