On a hot day and traveling in a car, which method of keeping the occupants comfortable with the A/C is more energy and fuel efficient?
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Set the thermostat to a lower temperature and keep fan speed to the lowest setting
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Set the thermostat to a slightly higher temperature and compensate by setting the fan to a higher speed so you can feel cool enough with the breeze
Mythbusters did a test on this comparing AC to driving with the windows open. The AC barely affected the fuel consumption, while the additional drag of open windows made a huge difference.
So because the difference between off and full blast is negligible, less than the wind resistance of open windows, I’d say it probably doesn’t matter what setting it’s on. Go ahead and blast it.
My AC makes a notable difference in fuel mileage, even taking into account, the fact of gasoline density between summer and winter
Like, just forgetting I have my defroster on in the winter now makes a notable difference in how much fuel it takes compared to just the arms and legs setting
He asked about fan speed, not open windows.
Right, my point was that having the air on at full blast was negligible, barely affecting the efficiency of the car. So the settings probably don’t matter very much.