Reduced gas mileage?!?! Come on now...
If you tilt open the sunroof and open a rear window about an inch, you get nice airflow. If you are concerned about messing up your hair, it won't happen...even at freeway speeds. If it gets a little too cold, just turn on the heated seats. A cool, gentle breeze with heated seats is the start of a nice drive.
Elroy
2000 S4