Wind deflectors.. how bad are they?

[cyclopathic]

any tests/articles on window deflectors, how much they increase/decrease Cd?

[wdb]

I loved the one I had on my Fit. That thing kept a metric ton of crap from ever hitting the windshield. I know because I drove the car for a while before getting it; I had a stone chip the first week, and I was lucky not to have more given the amount of guck bouncing off the poor thing. The before/after difference was dramatic.

Not exactly answering your question, I know. But in the case of that car it was a worthwhile tradeoff even if it did hurt MPGs.

[aerohead]

I've never seen an official test report.
One premise for them,was that you could crack the windows for ventilation and get away with not running the AC,theoretically saving energy.
Even in a Mediterranean climate,like Southern California,I'm not sure you'd get by.

[freebeard]

I like the wind wings on my car. They can go from closed and sealed, the default, to cranked wide open so they become scoops in the summer.