ROTFL....
OK, Seriously though the MAX setting? That has to use more fuel cause it damn near removed my hat the other day... That's a tool we must learn to use responsibly.
Bottom line IMHO, Why worry about fuel mileage? Seriously, are you going to STOP driving? No, are you going to swelter in the heat to save gas? No, so why spend one more second discussing the price of gas or whether or not this or that will get me an extra 4-5 MPG. Just doesn't matter, chances are you are not going to change your driving habits, you're not going to start riding the bus, and you're not driving a freaking Prius so obviously you are really NOT that worried about fuel mileage.
Unless we are just discussing it as small talk, kind of like the weather. In which case I'd have to agree with the others and it would make sense that your A/C running at and maintaining 60 deg would be working harder, placing a higher load on the engine, thus using a thimble or two more fuel than running it at 70deg.