I tested this theory this week. I drove to south bend using air with the windows up and averaged 37 MPG in my Saturn.

Then when I drove home I kept the Air off and opened both front windows, and I averaged 33 MPG.

Seems like a no brainer to me.

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Charles_Main

"Whenever a man has cast a longing eye on offices, a rottenness begins in his conduct."
Thomas Jefferson

"Dependence begets subservience and venality, suffocates the germ of virtue, and prepares fit tools for the designs of ambition."
Thomas Jefferson