OPINION

CAR TALK

DEAR CAR TALK: The other morning, I went out to start my Toyota Prius and go to work. The car started up fine (just the electronics come on), but as soon as the gasoline engine came on, there was a terrible, roaring noise.

When I pulled into my mechanic's shop, even before he looked at the car, he said "someone had her catalytic converter stolen." He was right. My whole tailpipe was gone! Why would someone do this? — Patty

DEAR READER: Why did Willie Sutton rob banks? Because that's where the money is.

All catalytic converters contain tiny amounts of some rare minerals: platinum, palladium and rhodium. In the past five years, rhodium has gone from about $600 an ounce to something like $30,000 an ounce. Or even more than the weed Snoop Dog likes. So, even in small quantities, rhodium is very valuable.

And, for some reason — presumably related to their small pollution footprint — Prius converters have more rhodium than other cars. So thieves are targeting Priuses in particular (though not exclusively), because their converters are worth hundreds of dollars.

Typically, a thief will sneak into a driveway, crawl under the car and use a large pipe cutter to cut the exhaust pipe right near the engine, just in front of the converter. Then he'll just take the whole exhaust system — the converter, the muffler and the tailpipe — and scram. The next morning, you get in your car, and it sounds like a Gatling gun.

And as I'm sure you know by now, Patty, a new aftermarket converter will cost you about $1,500. A new factory one from Toyota will cost $1,000 more than that. What can you do? Not much, unless you can train a family of poisonous snakes to live under your car.

In truth, it's going to take the recycling industry or law enforcement to clamp down on the resale market — to make it harder for thieves to resell stolen converters — before we'll see this trend subside. And the pressure to do that will likely come from insurance companies, who probably aren't happy about forking over millions of dollars in stolen converter claims.

DEAR CAR TALK: How important is it to change spark plugs? I have a 2012 Toyota RAV4 V6 with 100,000 miles on it. I was thinking about having the plugs changed until the dealer told me the price.

The plugs were going to cost $27 each. The labor was going to be over $500 and take three and a half hours. They said there is a cowl that has to be removed, which takes a lot of time. So how important is it to have the plugs changed, and is this a legit cost? — John

DEAR READER: That's what it costs, John.

On those rare, 6-cylinder RAV4s like yours, the three plugs that face the front of the car are easy to get to. But the other three are kind of crammed up against the firewall. To get access to them, you have to remove the intake plenum, which is underneath the "cowl" your dealer is talking about. As a result, it can be a three to four hour job, plus the cost of the iridium plugs.

Should you do it? It's a tough call. Toyota recommends you change the plugs every 90,000 miles. For most people, that means you do it once during the life of the car. But it's very expensive and not as clearly necessary as it once was.

Spark plugs rarely fail these days. We used to replace spark plugs every 12,000 miles, and they'd look like they were retrieved from an arson crime scene.

These days, plugs almost never go bad. They can last indefinitely. We see lots of cars in the shop with over 100,000 miles that still have their original spark plugs.

But here's the danger: If they're never removed, they can get stuck in the engine. They can, essentially, fuse to the cylinder head. And then, if one ever does fail, you're looking at a major engine repair and potentially thousands of dollars to replace ... one failed spark plug.

If the plugs were easily accessible, you could just loosen them and then tighten them back up — just to make sure you could remove them if you ever had to. But with the amount of work it takes to get to the rear plugs on your RAV4, you'd be crazy to do all that labor and not just replace those plugs for the additional $81.

So, as a responsible mechanic, and one with an IRA to fund, I have to recommend you go ahead and change them, especially if you plan to keep this car for the long haul. But as a consumer, I can certainly see why you'd be tempted to take your chances, John.

Ray Magliozzi dispenses advice about cars in Car Talk every Saturday. Email him by visiting cartalk.com

Upcoming Events