[RickwithaTbird]

also though, you have to consider how much are you rolling down the windows?

My A/C is broken. so on the highway if I'm doing 80, I have to open the windows to stay cool. But I simply pop my window open a couple inches, then I open the window behind it a couple inches more. There are ways to roll the windows down which create a lot of drag, and there are better ways to roll them down which create far less drag. You just have to experiment. I do 80-90 on the highway with windows down, and it's not even windy in my car, but it still allows the hot air to escape.