What’s the more cost-effective method of cooling my car? I could (A) nudge the temperature selector a tiny bit towards the “warm” side and put the blower on “high”, or (B) I could crank the temp lever all the way to “cold” and leave the fan on its lowest setting. Either way, the “A/C” and “recirculate air” buttons are on. Either way seems to cool the car just as quickly as the other, though I suspect that one method draws more power from the engine than the other.
FWIW, I’m in a 1995 Buick sedan, and it’s summer here in hot and humid Fort Worth.
It depends on what you’re doing, and at what time.
I usually open the windows for the first five minutes, and recirculate on a low fan setting after that.
However- and this is key- the engine continues to pass cold coolant through the air conditioning plumbing for a few minutes after you switch it off. At high speeds, enough air will be forced through the A/C induction system to keep the car cool for between 5 and 20 minutes, depending on the ambient temperature, your car, and your speed. So… after the car reaches a comfortable temperature at high speed, turn the recirculation off and turn off the blower; the car will stay cool with no additional power drain.
(I’m in equally hot and humid Orlando and this works on all but the hottest days at speed)
I’d say you’re splitting hairs. I seriously doubt data is available comparing various fan speeds with various temperature settings. If the info were available, I’d expect to possible savings of not more than a few hundredths of a mile per gallon.
Set the temp lever and the blower speed to where you’re comfortable and don’t worry about it.
The A/C system uses refrigerant. Coolant is used in the cooling system (radiator, water pump, heater, engine passages). Refrigerants are used to make something colder than ambient temperature. Coolants are used to reduce the heat in something that gets hotter than ambient temperature.
Setting the temp selector to cold and fan low will use less gas than setting the temp selector on medium and fan high.
The reason is based on the design of the HVAC (Heating, Ventilation, Air-Conditioning) system used in cars.
In a car, air enters from outside (or from the pass compartment in case of re-circ), and first goes through the AC Evaporator. The evaporator looks like a small radiator and when the AC is on, the Evaporator is cold (just above 32F). The air then goes either to the heater core (temp sel WARM), or directly to the vents (Temp sel COLD), or some each way (temp sel MEDIUM).
With the temp sel on medium and fan high you pass a large volume of air over the evaporator, cooling the air. You then warm it back up by passing some of it through the heater core.
With the temp sel on COLD and fan low you pass a much smaller volume of air over the evaporator.
The AC system will only run the compressor enough to achive the set evaporator temp (usually 33F-35F), at which point it will shut off.
With a smaller volume of air going through the evaporator the compressor has to run less to maintain the set temp, therefore saving some gas.
Is there enough difference for you to ever notice? Doubtful…