Vented Windows: Extra Drag?
 

On my Civic I have these rear vented windows. They are great around town when I'm traveling at slower speeds since they vent the rear hatch and help diminish the "parachute effect."

But what do you guys think happens at highways speeds with the front windows closed. I'll only travel highway speeds with the windows closed and cycle the AC on and off. But with cooler weather now in the Northeast I'm wondering if there's significant aero drag with the windows vented open.

https://www.fuelly.com/attachments/fo...fe77005c84.jpg

There should be, it will be a low pressure aera where air will probably travel into the cabin, not the other way around.

Furthermore, it will make the rear end of the car virtually "wider", which is always bad.

However, you will only see a difference (like with the windows down) probably only around 40mph or more. Anything below that and it will be negliable, or at least much better than having the A/C on...

So what about my theory that these windows decrease the parachute effect? This is with the front windows rolled down, and back windows vented open, and only driven around town 30mph - 50mph.

Think I'm correct with this thinking?

How about sunroofs that are opened "up"?

IIRC from a previous sunroof discussion, the up-opened sunroof isn't bad and may actually be good, due to the pattern of the air as it comes off the windshield.