Which mode takes more gas?

1. A/C's outside air vent closed?
2. A/C's outside air vent open?

Anyone know?

 

Neither,it is the same except that fresh air is being drawn in at the base of the windshield in fresh air mode .in recirc it is being drawn from a spot mear the glovebox.jens

 

I was thinking along the lines that if the air is being drawn from the outside, it would take more energy to cool it (Texas Heat is crazy), and if the air is being drawn from the inside, then it should take less energy to cool it down.

But I noticed that on older cars, if the outside vent is closed and the car is ideling at a light, the engine seems to be shaking alot more than when the air vent is open. So it would appear that the engine is working harder when the vent is closed, throwing my previous assumption out the window.

Anyone want to shed some more insight on this?