Skip Spark Plug Replacements at Your Own Risk

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 of 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

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.

Todays Car-o-Scope

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