Drag Coefficient with windows open?

[tdiggity]

Does anyone know how the drag coefficient of cars (or the model s specifically) changes with the windows open? Sure, there are a lot of combinations, but for simplicity sake, let's assume this:

Drag with windows closed = 0.24
Drag with driver+passenger window cracked open
Drag with driver+passenger windows fully open
Drag with all windows open

And lastly, what would the effect be on mileage? I'm in California with relatively nice weather, and so I want to know if I can go further if I opt to open the windows rather than using the air conditioning.

 

[Robert.Boston]

On nice days, I usually just run the vent, bringing in fresh air but without the additional noise or drag of opening a window. (Yes, on the Model S you can turn off the A/C while leaving the fans running.)

 

[mknox]

On nice days, I usually just run the vent, bringing in fresh air but without the additional noise or drag of opening a window. (Yes, on the Model S you can turn off the A/C while leaving the fans running.)

Ditto. I've heard it said that it is more efficient to use a/c with windows up than no a/c and windows down on the highway, but the reverse is true in the city.

 

[jerry33]

Ditto. I've heard it said that it is more efficient to use a/c with windows up than no a/c and windows down on the highway, but the reverse is true in the city.

A lot depends on the car and what speed "highway speed" is. Generally, whether it's more efficient or not, over about 55 mph tends to be too noisy with the windows open--even if they're only open a few cm.

 

[Norbert]

An interesting test would be if one of the Model S owners put the car on cruise control, and a passenger would write down (on a long even stretch of road) the Wh/miles display under various conditions...

 

[pilotSteve]

naah, they'd be too busy griping to the driver until s/he turned the AC back on