Growling Jetta likely has a problem with its leak test pump

Dear Car Talk:

I have a 2008 Volkswagen Jetta with 140,000 miles on it. I bought it in 2009 with 20,000 miles on it. I’ve never had any major issues with the car. But within the past couple of weeks, it has started to make a “growling” noise when I turn the car off. It growls for about 10 seconds after it’s turned off, and then goes quiet. Any ideas what this might be and what it costs to have it fixed? – Leslie

RAY: I think you might just be parking too close to the dog’s bed, Leslie. Try stopping a little sooner when you pull into the garage, and see if the growling stops. Actually, I think the growling is coming from your leak test pump. That’s part of the emissions system.

There’s a pump in the back of the car, near the gas tank, that goes on right after you shut off the engine. It pumps for about 10 seconds to pressurize the fuel system. If it’s able to get the system up to full pressure in the allotted amount of time, the computer concludes that there are no leaks, and all is right with the world. If it takes too long to pressurize the system, the computer concludes that there’s a leak somewhere, and it turns on your check engine light.

I’m guessing that something’s wrong with your pump after a mere 140,000 miles. It’s always run after you’ve shut off the car. But now it’s making noise because the pump’s motor, or one of its bearings, is dying. Or maybe something close to the pump is now touching it and vibrating when the pump runs. You should be so lucky, Leslie. It’s obviously still working, because if not, it would have turned on your check engine light. So it’s not an emergency. But the noise suggests it’s likely to fail sooner rather than later. When you factor in diagnostic time, parts and labor, you’ll probably put out between $200 to $300 (and one growling noise) when it’s all over.

Can’t fix an engine using thicker oil

Dear Car Talk:

I have a 1991 Ford F150 with 183,000 miles on it. I’ve been using brand-name conventional oil in it since day one. So far, I’m not having any oil-related issues, but when I buy oil, I see specially blended oils for “high-mileage engines,” meaning engines with 80,000 miles or more on them. Is there any real benefit to using special high-mileage oils, or is it safe to continue with a quality, conventional oil that meets the latest Society of Automotive Engineers (SAE) standards? – Steven

RAY: Generally speaking, most people do not need a high-mileage oil. In the old days, when your car was burning oil, people would suggest that you add really thick molasses-like oil to the engine, like some 20W-50 weight glop. The idea was that the thicker oil wouldn’t flow as easily, and therefore would have a harder time seeping past worn-out valve guides and valve guide seals and getting into the cylinders, where it was getting burned.

But – hello! – you want your oil to flow easily. Its job is to flow and splash, so it covers all of your moving parts and protects them. Plus, it rarely worked. A lot of oil-burning takes place because an engine’s piston rings are worn out, and thicker oil won’t fix that. Using thicker oil is also a particularly bad solution for modern cars. Not that you’re driving a particularly modern car, Steven, but let’s flatter it and call it modern for the sake of discussion.

Modern engines rely on the exact opposite of that 20W-50 glop. They use low-viscosity oils that splash easily all over the moving parts of the engine to make sure they’re all lubricated. They also count on low-viscosity oils to reduce friction and drag (the work of simply moving the engine parts through thicker oil), which improves mileage. If you look at the specs for new cars these days, they’re not calling for 20W-50 oils. They’re not even calling for 10W-30 oils. They use 0W-20 synthetic oils. That means it acts like a zero-weight oil when the engine is cold and a 20-weight oil when the engine is hot.

Some “high-mileage oils” now include an additive that’s supposed to help soften up hardened, leaky engine seals. So if one of your seals is leaking, you can try a high-mileage oil. But I wouldn’t expect it to perform miracles – any more than Geritol is going to suddenly get your great-grandfather back on the uneven parallel bars. Otherwise, I’d do exactly what you’re doing, and use the oil that the manufacturer recommends and that meets the current SAE standards. Or even consider a synthetic.

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