Because I get out early every morning and run the highways of North Texas with a bunch of rock-haulers....I don't know whether full or empty of gravel, but every morning every one is streaming gravel-dust-laden gray water. Additionally, they are quite happy to occupy both southbound lanes of the highway under the guise of "overtaking" for mile...after mile....after interminable mile......so on the rare morning that it is also foggy/misty, that gravel-water mixes with the thick moist air and makes for some interesting patterns:
The leaper splits the flow, head-on:

Note a bit of right-crosswind causing some pooling on the right side at the windscreen vs. the smooth-swept flow on the left side.
As it is channeled around the cabin, a bit of bending around the mirrors:

there is an updraft toward the roof along the sides:


More evidence of a right-xwind in the roof photo, note the flow generally is up the sides of the cabin, pushing toward center at the roofline, but a greater offset on the right side.


Slight evidence of the updraft at the back wing:


I believe this one shows the confluence of the updraft and the impingement of the higher pressure from the roof center as it spreads over the boot-lid, creating a concentrated stream aft down the top of each rear wing:

 

Judging by the last picture, the shape of the rear pillar was strategically designed to keep an unobstructed airflow over the fuel door so as to prevent debris collecting near the fuel fill.

 

Hi Aholbro1
Damm but that's got to be annoying...… So which highways are you driving on. I'd like to know so I can avoid them. I'm in Dallas/Plano.
It looks like you need to have an in-house car wash to take care of all that muck.
BigBoss in Dallas, TX

 

I'm so pleased I purchased that Wind Tunnel at Walmart when they had the half price offer.

Imagine the alternative of putting your paintwork through that every day!

That has got to be killing your black paint or is it so fine it's not even scratching?

Graham