I think like some of you said before, one of the great benefits of the spoiler that it directs air down the back of the SUV where without a spoiler, there will be no flow.
I don't have a spoiler. So I have to air flowing down the back window. I could be driving in the rain I would literally see the raindrop slowly move down my back window while driving 55-60 mph.
On a summer day, I opened the back window and my sun roof because the weather was great. What happened was the heat from my engine was being sucked into the car. I felt hot air coming in through my dash and by my feet. I know at the point my back window was creating great negative pressure in my cabin. When I pulled my back window half up, the heat still leaked through my dash, but not as much as before.
Did anyone experince this or is there something wrong with my runner?
Also, for those who have spoilers, did you encouter this before?