[aerohead]

You don't have anything backwards,however the distinction between what is happening with the golfball and the Imprezza is unfortunately like the old "apples and oranges" metaphor.With the small golfball,the manufacturer is forcibly creating a turbulent boundary layer,by virtue of including the dimples in it's dsign.As your article states,the wire trips the turbulent boundary layer and it immediately transitions into a turbulent boundary layer.And as mentioned,while posessing greater skin-friction drag,the smaller wake made available by virtue of the turbulent boundary layer,reduces the "profile" drag,which is the major drag component for blunt bodies,and overall drag is reduced.With cars,and above 20-mph,drag coefficients are constant and the car demonstrates turbulent boundary layer which cannot be removed by additional smoothing of the body.And thats a good thing! So for your Subaru,or any car,the flow close to the skin would not benefit from additional roughening in the forebody.If you could see your car in a wind-tunnel,you'd see that,for the exception of a very small area in front of the windshield,the airflow is attached to the body,and remains so until it reaches the rear edges,where it breaks away into the turbulent wake( very different than the turbulent boundary layer).You are paying for turbulence through the engine bay,around the wheel houses,under the car,and finally,the enormous wake behind the car,which because it is a wagon,is basically the size of the entire frontal area of the car.Since your cars front divides the airstream such that more air is channeled over the roof,you'd find that the local air velocity over the roof is significantly greater than what your speedometer is indicating.The recommendation to remove your roof rack is based on this fact that air up there is colliding with the rack at velocities greater than those some airplanes fly at.Your biggest problem is behind the car and I recommend you check out what MetroMPG,Basjoos,and others are doing.