I remember reading a long time ago on this forum someone said the best method (when driving by yourself) is to leave both windows (front and rear) open on the drivers side and this will reduce the drag coefficient because the wind comes in thru the drivers window and exits back out thru the rear window on the drivers side (backseat)
And from what i understand this is preferred over leaving the front driver and front passenger windows open (which is the traditional thing people do).
Has anyone compared the mpg numbers in an experiment? it is really worth doing? We are putting extra wear and tear on the rear windows motor compared to only leaving 1 window open out of 4: The front drivers window ONLY.