Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.
Today we’re taking on a listener question.
“Hi, my name is Megan Heinz. I have a question for Possibly. My child has a car pick up line. And I’m wondering if it’s better for me to turn the car on and off again as the line moves forward. Because I really don’t want to idle while I’m waiting.”
We had Albert Wu and Charlie Adams from our Possibly team look into this question.
Albert Wu: Hi, Megan!
Charlie Adams: Hey, Megan!
Megan Hall: So listener-Megan wants to know if repeatedly starting her car releases more emissions than just idling while she’s waiting in the pickup line at her son’s school. What did you find out?
Albert Wu: It turns out, the answer to this question really depends on the type of car you drive.. Megan mentioned that she had…
Megan Heinze: “a 2007 Volvo XC 90”
Albert Wu: … which is an older gas car.
Charlie Adams: In those types of cars, idling burns a constant, steady stream of gasoline to keep the engine running at the slowest rate possible without stalling. But starting the car also uses fuel.
Megan Hall: Which uses more fuel?
Albert Wu: It depends on how long you idle your car. A study by the Argonne National Lab found that the break-even point was about 10 seconds.
Charlie Adams: Basically, if you’re planning to idle your car for longer than 10 seconds, it’s better to shut off the engine and start when you need to move.
Megan Hall: Great, that sounds like a pretty simple answer! Just follow the 10 second rule!
Charlie Adams: Pretty much. It gets a little more complicated in freezing weather, because starting a cold engine requires more energy and creates more pollutants.
Albert Wu: But people usually keep their cars on in the winter to stay warm, anyway.
Megan Hall: What about all the wear and tear on your car from starting and stopping?
Albert Wu: You shouldn’t need to worry about that. It takes 5 to 10 minutes for all the oil to run back down to the pan, so restarting for the kind of wait times you’ll have in a school pickup line isn’t really an issue.
Megan Hall: So, what’s your advice for Megan?
Albert Wu: On most days, she’s better off turning her car off and restarting it when she needs to move up in the pick-up line, but on very cold days, she may be better off idling.
Megan Hall: Huh, so how big of a carbon dioxide emissions difference does turning her car off and on make? Would it make a big difference if she idled every day instead?
Charlie Adams: Turning her car off instead of idling would reduce her overall car emissions by around 1% per year.
Megan Hall: So, not a big deal?
Albert Wu: Well, for your personal emissions, that might sound small. But the same study found that if everyone in the US followed this rule, it would be the equivalent of taking five million cars off the road.
Charlie Adams: It’s a pretty easy thing to do, so I’d say, it’s worth the effort.
Megan Hall: But what about newer cars and hybrid cars? Does the ten second rule apply to them too?
Albert Wu: Most newer cars have something called an auto start-stop mechanism.
Megan Hall: What does that mean?
Albert Wu: They’re systems that automatically stop your engine when you press down on the brake pedal hard enough.
Charlie Adams: For those cars, you don’t have to worry about consciously turning the engine off and then on again. It’s stopped whenever you are!
Megan Hall: Do you also need to think about temperatures and wait times?
Albert Wu: That’s not necessary for newer models. Vehicles with the start-stop system have pumps that keep the engine hot while they’re stopped, and if the engine drops in temperature too much then it’ll automatically restart.
Megan Hall: Ok, so what’s the take-away here?
Charlie Adams: For older cars you should stop idling if you’re going to be still for longer than ten seconds, if it’s not super cold outside.
Albert Wu: And for many newer cars, there’s often no need to think about it at all- many manufacturers have done the work for you!
Megan Hall: Great, thanks Albert and Charlie!
That’s it for today. For more information, or to ask a question about the way your choices affect our planet, go to the public’s radio dot org slash possibly. Or subscribe to us wherever you get your podcasts.
You can also follow us on Twitter and Facebook at ask possibly.
Possibly is a co-production of Brown University’s Institute for Environment and Society, Brown’s Climate Solutions Initiative, and the Public’s Radio.
The post Should I idle my car or stop and restart? appeared first on TPR: The Public's Radio.