When using our car’s a/c is it better (less strain on the engine) to keep the fan high and the level of coolness moderate (closer to the middle, heading towards warm) – or the other way around (low fan and temp all the way to coldest)??
We’re about to leave on an 8-week car trip so would be great to know what’s better for our sweet Subie. Thanks!
It’s "the other way around."
The lower the fan speed, the less heat load for the compressor to deal with.
Use the recycle instead of fresh selection to reduce the moisture that it has to deal with.
Setting the temperature to warmer just adds more and more heat from the engine (heater core). It doesn’t reduce the amount of cooling.
Of course all of this will have little effect on gas mileage, and greater effect on your comfort. If you can’t afford the difference in gas, then you can’t afford the trip.
When the outlet temperature is turned away from the coldest setting warm air is blended into the plenum to get the temperature desired. That added heat must be absorbed and carried away. Energy is required to carry the heat away and additional stress is put on the system.
The only “settings” that make any real difference is “on” or “off”…
Your car is designed so that there is no way you can damage or stress your system beyond what it is designed to handle by either the temp,recirculate, or fan speeds you select.
Many A/C systems have the compressor working all the time, and the temperature is achieved by blending warm and cold air. Such a system uses the same power all the time; setting the fan lower reduces the electrical consumption by a very miniscule amount.
As mentioned elswhere, the only saving that’s mearurable is between “on” and “off”.
I would stop worrying and just set the unit to where you are most comfortable; the Rerculation setting is for quick initial cooling, and should not be used for an extended time; it could freeze up the evaporator.
Thanks everyone, this is all really good to know.
Last question if anyone has time: What about switching the AC on and off? Running it for 10 or 20 minutes till the car gets nice and cool, and then turning it off for 10 or 20 minutes. Would this make any difference, or is all the turning on and off doing more damage?
(We are independent musicians traveling lots for work, so any way to save $ and strain on the car is helpful – that’s why it sounds like we’re taking a road trip we can barely afford 
Thanks!!
If you don’t mind the “hot” and “cold” cycles, you would indeed save some money on gas by shutting it off. Regulating the temperature with the dash dial or fan speed, as mentioned, does not save any fuel.
Happy trails to you!
That would work, but you will find the cycles to be closer to 1 to 2 minutes instead of 10 to 20.
The car could absolutely care less.
You won’t see any significant fuel savings with any strategy. Leave it on a comfortable temperature. You are on vacation enjoy it.
Caddyman is 100% correct. There is little to no difference in what speed the fan is set at…Just having the AC On is the biggest factor.