[aerohead]

Originally Posted by euromodder

BMW did something similar years ago on some models, with small semi-circular bulges in the gap between the mirror and the side windows.

I don't recall the car types, but I've seen more of these on mirrors.
The mirrors on the Volvo V50/S40 have a small boattail

So apparently, some manufacturers are taking measures to cut down the drag from the mirrors.

They're also going after wind noise.