The article says that edmonds did a study on the fuel economy with A/C on/off and the windows up/down and found no 'significant' impact (not that there is 'no' impact at all).

I think one of the reasons the windows and A/C myths are so commonly believed is because they seem to make logical since. Taking a step back and thinking more about it, it does make since that there would be 'minimal' impact on the fuel economy on a car that has a 200hp, 300hp+ and other high hp engines.

I'm by no means a engineer nor have ever done any kind of first-hand research on this. But based on my past experience, I mentioned in earlier post, and considering what they say about not a 'significant' impact, it seems very reasonable to me.