Q: I recently purchased a 2017 Hyundai Elantra, which I love. Heading eastbound (downwind), I have been known to get 50 mpg on the highway. But there's one thing about it I don't understand. While sitting in the driveway listening to the last 10 minutes of your radio show, Car Talk, I get a "low battery" warning, and I am directed to restart the engine.

Thirty years ago we could sit through a double feature at the drive-in, listening on the radio with the ignition switch on "accessory" and still start the car later. What's changed? - David

What's changed is that you now have a computer in your car that can remind you when you're running down your battery. And the computer can take preventive action and shut down your car if you don't respond to its warning.

A: Next time you see this warning, try ignoring it. What you'll probably find is that after a few more minutes, the car will shut itself off. It'll probably give you another warning first, and say something like, "Shutting down soon, David. I mean it."

As a side benefit, when it does shut down, our show will be cut off and you won't have to listen to rest of it.

Why would the car's computer be programmed to do that? Well, here's one scenario: Your car has keyless ignition. Let's say you park the car but you accidentally hit the "start-stop" button twice when getting out. So instead of shutting off the car, you've left it in accessory mode.

So the car sits there for 10 or 15 minutes, and then says, "Hey, David, you still here?" If you're there and just listening to the radio waiting for your wife to clean out the shoe rack at Target, you can restart the car for 30 seconds and keep listening.

But if you're not there ... if you're already inside watching Geraldo while nursing a growler of Shark Spit Lager, your lack of response will cause the car to shut itself off to save the battery.

And while listening to the radio for 10 or 15 minutes would never run down your battery, it's possible that if you left the car in accessory mode from 7 p.m. to 7 a.m. you might. So it's the car looking out for its own best interests, David. It's the Hyundai Elantra Selfish Edition.

Q: 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

A: 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.


Got a question about cars? Write to Ray in care of King Features, 628 Virginia Drive, Orlando, FL 32803, or email by visiting the Car Talk website at www.cartalk.com.

(c) 2019 by Ray Magliozzi and Doug Berman

Distributed by King Features Syndicate, Inc.

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