I’ve looked up a lot of sites none of them talk about how much gasoline is used when you keep your temperature at the highest or coldest in your automobile? If it does at all.
It does not talk about it because if it did measuring would be impossible . I seriously doubt if it makes 1 mile per gallon difference.
Running the AC on max cold probably uses a little extra gas. It may seem counter-intuitive, but takes energy to produce the cold air, and the only energy source is the gasoline. So the colder the AC air, the more gasoline consumed. But I doubt it would be a big difference.
Don’t most late model cars closely control the HVAC temperature by blending heated air with the cooled air? And when on MAX the heat is totally eliminated? On such systems the compressor would work less on MAX than on some specified temperature warmer than what MAX provides it would seem.
The AC compressor picks up refrigerant at about 30psi and compresses it to 200+ psi, sometimes in excess of 350 psi when dealing with extreme heat. The most economical (as in least stress on the system while cooling the cabin) would be to set the system on MAX and regulate comfort with the fan speed.
Probably more like 1 mile per tank
I have also heard that the most efficient way to cool is to run the system on the coldest temp setting but run the fan on a lower speed. This also removes the most humidity as well as lots of air blowing over the coils can re-evaporate condensed moisture before it can drain.
Either way, I doubt this makes enough difference to worry about. Run it however you feel most comfortable and go on with life.
I would like to think it would not make much difference if any in your mileage. In non climate controlled vehicles the temperature is adjusted when the ac is on by allowing coolant from the engine through the heater core. That being said, you are just adding heat to keep it from getting too cold inside. Depending on which side of the evaporator core the heater core is perhaps could cause less or more strain on ac compressor. If the heater core is on the afterward side of air flow through the cores then I would say it has no affect whatsoever. But keep in mind, I am not educated in this field of hvac and it’s just my theory.
P.S. I am not certain how climate control units work, if diversion of air or actual control of compressor or expansion valve or control of coolant.
Most use a blend door to blend hot and cold air these days. The AC compressor on cars is either on or off from what I understand. There is no variable speed or pressure like on a household unit. There is just a magnetic clutch that kicks them on or off.
That being said, there will be less load on the compressor if you run the fan on low. I doubt this matters on any new car but did read about how in the old days you weren’t supposed to keep the AC on max for more than a few minutes at a time.
A compressor will work harder if you have the inside temp set very cold and the outside temp is hotter. Running the fan on low will effectively reduce that difference.