Probably an obvious question, but I never had a car where you set the temperature, and the A/C system adjusts the cooling/heating and fan output power automatically. My question is that if you have it on the auto setting in the winter, does this negatively impact the gas mileage (as when cooling in the summer) because the A/C LED is on even though it will only be pushing out heat? I assume not, but though it best to clarify.
Not a stupid question at all. Many people in some area's (North) of the country believe (falsely) that AC means cool air. It really means Air Conditioning, which also controls humidity, it "conditions" the air. So in winter when the AC (LED) is on, the compressor will be running even though warm air is coming out. This will affect gas mileage. However your air will be less damp and at times windows less foggy & it's important to run your AC during the winter to keep the seals lubricated. People up North, (North West in my experience. Frequently get less life out of their AC systems because of thinking AC only means cooling. Seals dry up from lack of use. Of course this isn't everyone, I'm making broad generalizations based upon my experience with family members and friends, no offense to anyone of any particular region. Hope this helps.
I tend to activate AC in wet conditions only when desparate, ie: other measures have failed and it's fogging up. When using AC in hot conditions, I'll indirectly control fan speed, by setting the system on Auto, then raising temperature setting until the fan "calms down", running at 2~3 bars max. Then as the interior cools I might drop it a bit, just 'till it's comfortable. With any AC system, it's a good idea to run it say once a month at the most, just to keep the internal fluids circulated.
Since the Prius uses an electric compressor, I am thinking it is a hermetic unit and does not have any gaskets to dry out.
