Dear Car Talk:
My husband tends to leave the cruise control on after driving my car (and who knows how often he does this with his own car?).
What are the negative effects of this practice? I assume there are some, or manufacturers wouldn’t give us the option of turning the cruise control switch on and off.
Am I right in this assumption?
— Carrie
I’d be much more worried about him leaving the oven on, Carrie.
He’s actually not doing any harm to the car by shutting off the engine with the cruise control main switch still on.
Here’s why: The primary purpose of the cruise control’s main “on-off” switch is not to get you to turn it off. It’s to force you to turn it on.
It’s a safety step. Most cars have switches to set or resume the cruise control on the steering wheel or one of the column stalks. They’re located there for your convenience, making them easy to reach. But, as you can imagine, making them that convenient can also make it easy to hit one of those buttons by accident.
To make the system a little safer, the car, by default, always starts with the main cruise control switch turned off. That way, if your finger accidentally hits the “resume” button instead of the “volume up” button, nothing bad will happen. The car won’t suddenly speed up and cause you to panic. To get the cruise control to work, each time you drive the car, you have to affirmatively turn on the main cruise control switch first. Then those steering wheel controls will work.
So, when your husband shuts off the engine — even if the cruise control main switch is still on — rest assured the cruise control will turn itself off.
You can test this for yourself, Carrie. Next time your husband commits his cruise control crime, have a look the next time you drive the car. The cruise control will be off. And you can reassure your husband that they had him in mind when they made the system idiot proof, Carrie.
Dear Car Talk:
According to my Chevrolet service department, the turbo charger on my 2016 Silverado 2500 HD Duramax needs to be replaced due to excessive carbon buildup.
It only has 37,000 miles on it. Should I go with the new turbo charger costing almost $5,000 from the dealer, or do I go with a local diesel shop that can remove, clean, and replace it for about a quarter of the price?
Chevrolet can’t tell me if a new turbo charger will be more resistant to carbon buildup or whether the same thing will happen to the new turbo.
I do pull a fifth-wheel trailer. Is there anything I can do to prevent this from happening in the future? Thanks.
— Jerry
Condolences, Jerry. The first thing I’d do is talk to your dealer, or to Chevrolet, and ask them if they’d be willing to help you out here.
While your warranty has expired, a turbo charger shouldn’t fail at 37,000 miles. That’s ridiculous.
You should appeal to their sense of fairness and responsibility, and see if they’ll pay for half, or at least make some meaningful contribution to the repair.
They may argue that you’ve been pulling a trailer, and that puts extra wear on the turbo. That’s true, but you bought a diesel 2500 truck, which is designed to pull a trailer. If Chevrolet reduces the cost to where it’s anywhere near the cost of a rebuild, I’d get the new turbo.
But if not, I’d do the rebuild for a quarter of the price. As you say, there’s no guarantee that the new turbo will last more than 37,000 miles. And you can rebuild the turbo four times for the price of replacing it once.
In terms of preventing future failure, if your turbo was defective, there’s nothing you could have done to prevent this. But in the old days, turbos would sometimes get choked up with oil if they weren’t allowed to cool down sufficiently after hard use.
That problem was largely solved by synthetic oil and better manufacturing. But allowing the turbo to cool down after hard use can’t hurt.
So, after pulling your trailer or doing any mountain climbing or hard driving, try letting the truck idle for a few minutes, before shutting it off. That’ll allow the oil to circulate and cool off. Maybe that’ll extend the life of your next turbo to 38,000 miles, Jerry. Good luck.
