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Saving gas with air conditioning?

When the air conditioning gets too cold in the car, we can either adjust the fan speed (slower) or adjust the temperature (turn it a bit warmer). I am wondering which choice is better for saving on gas mileage.

Probably no real difference, the compressor runs about the same either way.

+1 for texases.

Makes no difference with most cars. Some get the car cold and then shut the AC off for a while until it gets too warm. This saves some energy since there is no drag of the compressor when it`s off.

Yep no difference. The air conditioning compressor (which takes the additional fuel) is running the same regardless of the heat setting or fan speed. Only way to save anything is to shut it off completely to vent, but then if you open the windows, the wind drag will cost more than the air conditioning. So just enjoy and don’t worry about it. You deserve to be cool in the summer and will arrive at your destination refreshed and not needing a shower.

You guys are right, but awhile back there was a lot of conflicting entries about this subject. I have had many cars since my first A/C car in 1966 (Dodge Monoco 9 pass. SW) and on all of them thecompressor ran all the time the A/C was on.
You surely don’t need the A/C this time of year, do you?

I agree. All you are doing with the air on while turning the temp gauge up is mixing the air. The compressor doesn’t know the difference. I agree too that you don’t need the air in the winter all the time. Of course there are some times for moisture control that you do.

I was told by a air conditioning specialist years ago where I was having work done, that he sees as many problems with leaks in the systems from people who don’t use the conditioner enough. They let it sit all winter which keeps seals from swelling and staying tight. I believe him and always reminded my wife and kids when driving our cars, to use the air for about twenty minutes a couple times a week. Maybe it’'s different now, who knows? I leave treated gas in carbs of my small motors too over the winter for the same reason.

All cars I have had since 1966 ran the A/C compressor when the defrost is on. I guess not all cars do.

“use the air for about twenty minutes a couple times a week”

I’ve heard that 10 minutes once a month will do the trick.

Elly, the thread that I think you are referring to was about a caller into the show who had a friend who would not use the heater in winter because it used gas. Most of the discussion was purely theoretical, but almost all agreed that any additional fuel used would be so small that it would be undetectable buy the owner.

In theory, I think that turning down the fan speed would use less gas, but I don’t think that it would use enough less to be detected by any normal means. It would take some very sensitive scientific testing equipment to validate or invalidate that theory. I don’t have access to that.

BTW, I had a 66 Dodge Coronet SW, great car.

On my cars at least in Minnesota, the compressor won’t come on if its colder than somewhere around 28-32 F, which is most of the winter.

Well Kieth, anything electrical that you turn off will save energy, no matter how little it is. and remove the power steering, pull the mirrows back, keep the windows up, drive alone in the car, drive slowely, all these increase the gas mileage, but very little.

And Bing, Most, if not all, the cars I have had since 1966, ran the A/C with the defroster regardless of the temperature.

Well Elly, we are in agreement on your first paragraph. I have not had exactly the same experience you have had with regard to your second paragraph. Only a few of mine did, but although I sold the 66 Dodge in 1992, it seems that I recall that its AC did come on in full defrost mode, but not in the split defrost mode, same as my Saturn.

Every car I’ve ever owned has run the A/C with the defrost too, though some “foreign” cars apparently don’t. And gawd, I hope we’re not starting that discussion up again…

IMHO, you might save a very SLIGHT amount of energy if you turn down the fan speed–my rationale for this is if you turn down the fan, the evaporator coil will begin to get too cold and the system will shut off the compressor for a bit. (or on some vehicles that use a variable displacement compressor, they will adjust the compressor output) If you just turn the temp to warmer, the blend door will just add hot air to the cold, and the compressor may run a bit more.

Of course if you have climate control, you can just set it an forget it, and the computer will make the decision on when to run the compressor, so if the system was designed and programmed right, this type of system may save the most. But really, you will likely save more money if you just make sure your tires are inflated properly and your car’s alignment is correct.

Please, again, any savings are going to be more theoretical than measurable. In the end, I don’t think it matters which choice you make, so make yourself comfortable. If you really want to save gas, don’t drive.