Relax, Dad – the car’s got this whole ‘starting’ thing figured out

Dear Car Talk:

My family thinks I’m crazy. But I think it is a good idea to power down the radio and the air conditioning controls in the car before turning off the engine. My reasoning is that when I go to start the car again, it will be easier on the car’s systems.

Am I on the right track, or just a dad whose kids think he should worry about something else? – Chris

RAY: I'm afraid we're going to have to side with your family here, Chris.

I mean, you’re right that it takes a lot of battery power to start an engine. That’s the single most power-intensive thing the battery has to do. So it makes sense that if the battery doesn’t have to simultaneously run the air conditioning, the radio and the in-dash espresso maker while it’s trying to start the car, that’s better, right?

Right. But what you don’t know is that the car takes care of that all by itself. When you turn the key to the “start” position (or push the start button in newer cars), all of the car’s power-intensive accessories are temporarily shut off until the engine starts.

You can see this for yourself. Try leaving all that stuff on. As the car is cranking, your wipers, AC and fan blower will momentarily turn off. Then they’ll resume once the engine is running.

And if you start the car at night with the lights on, you’ll see the lights dim as power is shunted toward the starter, where it’s needed.

So, congratulations, you are now free to worry about other things, Chris. If you’re not sure what to worry about next, ask your family for the full list of the reasons they think you’re crazy, and move on to No. 2.

Modern tanks don’t gather debris

Dear Car Talk:

I’ve always been told not to run my gas tank to empty. Not because I might get stuck, but because the fuel pump will pick up trash at the bottom of the tank and cause the filter to clog up.

Is this still true? Or is it no longer true for newer models? Remember, not all of us drive newer cars. – Ann

RAY: Well, if you're still driving your 1937 Duesenberg, Ann, it's probably good advice. But if you're driving a car that was made within the past four or five decades, picking up "junk" at the bottom of the tank is not something you have to worry about.

There are several reasons why it’s a nonissue. First, the pick-up tube itself has a fine-mesh sock on it. That allows liquid gasoline to pass through, but stops any debris large enough to damage the pump or the injectors.

I suppose if you had enough crud in your tank, you could conceivably clog up that sock. But you’d have to have the wreck of the Edmund Fitzgerald in there to do that.

Plastic gas tanks also have made a difference. They’re very common in cars now. And increasingly common at gas stations, too, where the fuel is stored. So while old steel tanks could rust and produce flecks of metal when they get old, plastic is forever – fortunately and unfortunately.

And, finally, gasoline itself has gotten cleaner. When manufacturers made a massive shift to fuel injection, starting in the 1980s, many of them demanded that the oil companies make cleaner fuel.

They didn’t want the tiny passages of their expensive new fuel injectors to get clogged up. And they especially didn’t want to have to replace them for customers under warranty.

So a bunch of manufacturers created their own fuel standard, called “Top Tier Detergent Gasoline.” It had to have extra detergents and no metallic additives. And most major oil companies complied and made the stuff.

Then, over the past dozen or so years, thanks to EPA regulations, gasoline has gotten cleaner still.

We used to routinely see fuel filters plugged up after 30,000 miles. These days, we hardly ever see that. In fact, after we replace a fuel filter, we’ll sometimes cut open the old one, just out of curiosity. And usually there’s more debris on the meatball sub we bought for lunch than there is in the fuel filter.

So you’re not going to suck up any junk from your fuel tank if you run it to empty these days, Ann. You might get stranded and robbed by highwaymen. But your injectors will be fine.

About the Author