Your Engine Won't Care if it Turns off -- but you Might

Dear Car Talk

Dear Car Talk | Nov 05, 2019

Dear Car Talk:

We have a 2017 Ford F-150. It has a gas-saving feature that turns the engine off when we stop at a traffic light for more than a couple seconds.

My husband turns the switch for this feature to "off" every time he starts the truck. He thinks it's hard on the engine to stop and start over and over.

If that's true, why is it offered as a feature? I agree that what he thinks makes sense, but I'm confused as to why it came with the truck then (I always leave the feature on, mostly because I forget about it until I stop).

What is the answer? I enjoy your column very much. Thank you. -- Cathy



The reason almost all new cars come with automatic stop-start systems is because they save fuel and cut down on pollution.

They're especially useful in cities, where cars spend an inordinate amount of time sitting still, like 4,000-pound mobile air conditioners. But even in suburban and rural areas, there's no good reason to waste fuel and pollute the air while you sit, doing nothing, for 60 or 90 seconds at a traffic light.

The reason they offer an "off" switch for this feature is because, depending on how well it's executed, the stopping and starting of the car can be annoying to the driver. We drove a Chevy Traverse where the stop-start system was practically undetectable. The next week, we drove a Subaru Forrester in which it drove us bonkers and made the whole car shudder every time it restarted.

To answer your husbands concern, the engine really couldn't care less how many times you start and stop it. In fact, the less it runs, the longer it lasts. So arguably, you're prolonging the life of the engine by allowing it to shut off regularly.

There was some concern that these systems might lead to early failure of starter motors. In reality, we just haven't seen those problems yet. It's possible they'll develop in the coming years. And, in fact, if your husband is really convinced they will, he might want to put your IRA in starter-motor futures. But, given the big picture, and the positive effect these things have on the air we breathe, my advice to your husband would be to use the system, unless it drives him crazy.

Of course, he won't take my advice, so that'll be my advice to you, Cathy. We'll make you a bumper sticker. "Save the planet: Don't turn off the stop-start feature."


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