There's Only One Way to Cheap out on Car AC

Dear Car Talk

Dear Car Talk | Feb 20, 2019

Dear Car Talk:

I am cheap. Starting out on a hot day, I turn the air conditioner on. I set the AC to "max," I turn the temperature all the way down, and I set the fan on "high."

When it gets too cool, I first turn off "max." And then when it gets too cool again, what should I do? Remember, I AM CHEAP!

Should I turn down the fan? Is the AC still running full blast and I'm just not getting all that I'm paying for? Or should I turn up the temperature and set it a little warmer?

Is the AC cutting in and out as needed, like the AC in my house? Or are they just mixing in a little hot air if I turn up the temperature?

What should I do? I love your old show, which I still listen to every week. Thanks. -- Ken

You should go out and buy yourself a pair of Egyptian cotton Bermuda shorts, Ken. And drive around with the AC off.

Actually, the answer to your question is it doesn't really matter. In terms of what it's costing you (which is the essence of your question), none of the actions you list here are going to save you any money.

The AC in your car does cycle on and off, like the AC in your house. That happens regardless of how you set the temperature. The fan speed has no bearing on how hard the AC works. It just blows softer or harder and changes how much cold air you feel blowing on you.

Turning off the "max" setting doesn't save you anything either. When you set the AC to "max" (also called "recirculate" on some cars), it simply recirculates more of the air in the cabin that it has already cooled, and draws in less warm air from outside the car. That helps to cool the cabin faster, but doesn't change the power demand.

If you turn up the temperature setting, that won't save you any money either. It'll just blend in some warm air to raise the temperature while the AC pumps away. In fact, that's what automatic climate control systems in cars do. To maintain your chosen temperature, they'll run the AC and blend in more or less warm air to keep the temperature constant.

I'm sure you don't have an automatic climate control system in your car, Ken, because you're what? Cheap! So the only way you'll save any money is by turning off the AC entirely. That will reduce the demand on the engine, which will increase your mileage a bit, which will ultimately save you a few bucks at the pump.

Oh, but I almost forgot to mention: You can't open the windows. If you open the windows at moderate to high speeds, you'll mess up the airflow around your car and make it less aerodynamic. That'll more than wipe out any increase in mileage you get by turning off the air conditioning.

So you can only open the windows in stop-and-go traffic, when there's no breeze. How's that sound, Ken? But that's how you can save money. Turn off the AC and keep the windows rolled up.

Just be aware that your wife's going to divorce you due to the way you smell every time you get home, so don't forget to subtract alimony from all of your savings. Good luck, brother.

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