Why do the pros tighten everything so tight?

Dear Car Talk:

I’ve changed my own oil for many years now (less and less as I get older and when the outside temperature is cold). It’s one of the few things I can do anymore. My question: Why do oil places have to tighten the drain bolt and filter so tight? My dad taught me to tighten the drain bolt finger tight and then just a little more; for the oil filter, hand-tighten it and then turn it another half-turn. I’ve never had either one leak on me. However, when I’m the next one to change my oil after the pros, I have to use a 12-inch pipe as a wrench extender, along with a hammer, to loosen the bolt. I also have to use several varieties of filter wrenches to loosen the filter. How come? – David

RAY: Well, it could have something to do with your advancing age, David. How often do you have to use that oil-filter wrench these days to open a jar of applesauce?

Mazda3: Different looks for different folks

Actually, the reason those guys tend to overtighten the drain plug and filter is due to painful experience. Several years ago, Rocko the oil-change guy got distracted and let some guy drive away with a loose drain plug. A few days later, the guy was back, demanding that his boss at Pokey Lube pay for his engine – which had seized up. And the boss took it out of Rocko’s paycheck.

So ever since then, Rocko says, “K, Mr. Funnyman, let’s see you leak oil now!” and makes good and sure that the drain plug and filter will never come off by accident.

Unfortunately, you can do damage by overtightening things, too. If you over-tighten the drain plug, you can strip the threads. And while it’s harder to do, you can damage the rubber gasket atop the oil filter if you really overtighten it.

Most likely, though, it’s just going to make it really difficult for the next guy to remove the plug and filter. And I guess Rocko, and his brethren, are counting on someone else being the next guy.

But I don’t think they’re doing it maliciously, David. They’re just erring on the side of too tight rather than too loose.

There is a happy medium, of course. And you’ve come pretty close to identifying it. In the shop, we tighten the oil plug about as much as we tighten a spark plug. I don’t know what that is, but it’s probably in the neighborhood of 20-30 foot-pounds of torque. I’d describe it as “hand tight, plus a little more.”

And for oil filters, we suggest tightening it as tight as you can get it by hand – so you turn it until it stops naturally, and then you might be able to twist it another quarter of a turn.

And if you have to use a 12-inch breaker bar to get it off, then back off a little next time.

Finicky convertible top might not be expensive to fix after all

Dear Car Talk:

I have a friend who owns a 2009 Nissan 350Z. He’s having trouble with the convertible-top mechanism, which puts the top up and down. Periodically, it simply does not work. The cost to diagnose this problem and fix it is estimated to be over $2,000. Can he simply disconnect the automatic mechanism for the top and raise and lower it manually? – Larry

RAY: It can be done, Larry. But it’s not easy – you don’t just unplug the motor and, voila, you’ve got a manually operated top. There’s a hydraulic motor and a bunch of hydraulic lines, and removing all that stuff is a messy and difficult job.

Your friend may be able to get it fixed for a lot less than $2,000. Instead of going to the dealer – where they’re likely to just replace the whole system – he should find a shop that specializes in convertible-top repair. There are shops like that in most major areas, and they do nothing all day but fix convertible tops. That’s the kind of place you want.

It’s not my area of expertise. My brother had a ‘74 Caprice Classic Convertible, and when his top stopped working, he just left it down and let the car fill up with water. And then leaves. And then snow. And then, in the spring, a family of raccoons.

But we did ask a guy who’s worked on convertible tops for 30 years: James Thompson, of Topless Auto in Chattanooga (who probably has some walk-in customers who are disappointed to discover that he’s in the car business).

He says the most common problem he sees with 350Z tops is bad brushes on the lift motor. If that’s your friend’s problem, the brushes may be able to be replaced, or, at worst, he’d need a new lift motor. But either way, it’s well short of $2,000.

And it’s much more impressive on dates. You simply push the button and the top goes down. That’s much more elegant than getting out of the car and grunting while you smear bird droppings all over your tuxedo.

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