Which one is more energy/fuel efficient to cool the inside of the car: lower thermostat + lower fan speed, or slightly higher thermostat + higher fan speed?
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
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I thought they found that it only mattered when the car was moving over 45mph that open windows caused enough drag to affect fuel more than AC?
It was. Wind resistances starts picking up at 30mph, becomes an actual factor around 40, and by 50mph makes a pretty huge difference.
It also depends on your car and what windows are open and how much. American cars tend to be pretty good about having the windows rolled down, but my Outback is AWFUL with the windows down at speed.
Aerodynamic drag increases with the square of velocity so the math checks out. Every additional 10mph is going to have a far greater impact than those before.
Honestly, I don't remember all the details. But that would make sense.