Modern cars aren’t hurt by idling to warm up

Modern cars aren’t hurt by idling to warm up

Dear Car Talk:

When I was a young lad learning to drive in Pennsylvania in the winter, I was always told that the best way to warm up a car on a cold morning was to start it, then drive away immediately but gently. It was common wisdom that to let it idle was to decrease the life of the engine, since nothing warmed up quickly enough: The moisture in the exhaust would condense more and rust the muffler; the oil would be sluggish, and thus the lubrication incomplete in the engine. Now we have cars with remote starters, and we are encouraged to start the car as we sit sipping our morning coffee in our jammies, so that the car is a tropical paradise when we finally start out on those cold winter mornings. What has changed? Are cars really designed for that abuse? Is it another case of planned obsolescence? Or is it a case of our laziness winning out over good car sense? – Richard

RAY: Historically, laziness always prevails, Richard. But these days, it’s not doing much harm to the car.

In the old days, when you started a cold car, the carburetor would pour gasoline into the cylinders almost indiscriminately – as if you were pouring it from a boot. Then unburned gasoline not only would come out the tailpipe and cause smog, but it also would find its way past the piston rings and mix with your oil. That meant your engine was being lubricated with gasoline and oil, instead of just oil – and gas is not nearly as good a lubricant. So the engine would suffer.

But these days, all cars are fuel-injected, so the fuel is very carefully metered. Sophisticated pollution-control systems ensure that only the precise amount of fuel that’s needed goes into the cylinders.

So, do you harm your car by warming it up in the driveway for 20 minutes nowadays? Not really. Obviously, you’re putting a small amount of wear and tear on the engine by running it when it would otherwise be doing nothing. But gasoline no longer dilutes the oil. And the moisture in the exhaust system is an issue only if you run the car for a brief period and then shut it off. If you drive away, that moisture will eventually evaporate.

The biggest issue, really, is that you’re wasting fuel and creating more pollution than you would have if the car were off.

But the pull of an 80-degree car interior on an 8-degree morning often is powerful enough to outweigh the 30 cents’ worth of gas you waste, and the ten-thousandth-inch sea rise you’re personally causing.

You’re still right, Richard, that the best way to warm up your car is to start it up, and if it starts, gently drive away. A car warms up faster when it’s driven, generates less wear and tear, wastes less fuel and pollutes less.

But no excessive mechanical harm is done to the car by warming it up in the driveway anymore.

Why are these new tires so leaky?

Dear Car Talk:

Since replacing the tires on my car 18 months ago, I’ve experienced several flats. The tires are Goodyear Fuel-Max. When I bring the car back to the tire shop, they inspect the tire and find no puncture. The only reason the mechanics at the shop and I can come up with is that the bar-code labels positioned along the bead of the tire are causing the seal to break. Could there be any other reason? – Frank

RAY: There shouldn’t be any bar-code labels on the bead, Frank. The bead is supposed to be 100 percent dead clean when you mount the tire. Otherwise, the tire won’t seat properly, and air will leak out.

So there’s nothing permanently embossed on or etched into the tire that interferes with the bead. And if there’s a removable label of some kind that came with the tire, the installer should have removed it. If not, that’s a real rookie mistake, and that’s on him.

Assuming the bead was, in fact, clean when the tire was mounted, then you’d look for either a bad air valve or some problem with the rim that was preventing the tire from seating properly. On an older car, that could be rust or corrosion. Or on a car of any age, it could be a bent, warped or cracked rim; I doubt the problem is with the tires themselves.

So if you’ve been back to the installer more than once with non-punctured flat tires, have them remove and remount the tires.

If you have an older car, without a tire-pressure monitoring system (TPMS), you can ask them to replace the air valves, too. Those older valves are a couple of bucks each. On newer cars, the tire-pressure sensors are built into the air valves, making those too expensive to replace without evidence that they’re faulty.

But while the tires are off, they can check again and make sure there are no dents or corrosion along the beads that are causing your leaks. Or if they find a price tag there, they can discreetly remove it.

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