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‘Leave the Car Running’ Feature

Today as I was running a very quick errand - a task that takes two to three minutes - I considered leaving the car running. People do this all the time, like when they want to run inside their house to grab the coupon they forgot or their cell phone or whatever, or when they want to run into a gas station to grab a pack of smokes or whatever. The problem with leaving your car running is that you really should lock it or else it's pretty easy to steal.

I've heard that turning on your car uses about five minutes' worth of gas.

So imagine this: I pull up somewhere, press a button that keeps the car running for five minutes, grab my stuff (say, envelopes to mail), and then take my keys out of the ignition and lock the car. If I don't return within five minutes, the car shuts off. Without the key it cannot be unlocked or shifted from park.

It's safer than leaving your keys in the car and it saves gas. Right? Go ahead and tell me why this idea is stupid, because aside from reasons that include "some idiot" and "lawsuit," I can't really think of any right now.

14 Responses to "‘Leave the Car Running’ Feature"

  1. Here in ol' Switzerland, they tell us that turning off your car even for only 20 seconds or so makes a big difference because of reduced pollution. (Typically, these 20 seconds might be the time you wait before a traffic light)

    This seems contradictory to your "turning on your car uses about five minutes' worth of gas." and I wonder if there is someone who can clear this?!

  2. In germany cars starting to have an auto-turn-off feature. While waiting in front of a traffic light for longer than 20s, the car is automatically turned off. With releasing the brake, the car turns itself on again. There are still a few problems with this technology I've heard. I don't have such a car myself.

    I've read even starting and stopping the car repeatedly, uses a lot less gas than leaving the motor running. So with modern cars, it's almost always better to turn the motor off.

    It wasn't easy to find some english references for my statements:

  3. The previous commenters are correct, but if you still want a "5 minute run timer" on your car, get a turbo timer. Sure, its main purpose is cooling a turbo, and your Touareg doesn't have one of those, but it should still work for you.

  4. Another vote for turning off the car:

    "Don't let your car idle for more than a minute. During start-up, your engine burns extra gasoline. However, letting your engine idle for more than a minute burns more fuel than turning off the engine and restarting it."


  5. I just read in the paper, not 3 weeks ago, (Winnipeg Free Press) that starting your car only uses up 10 seconds worth of fuel.

    I used to be a firm believer that it used more like 3-4 minutes worth of fuel. When you think about it though, that would be a lot of gas burnt up in such a short period.

    Why would it take so much fuel just to start your engine? There's already gas permeating your fuel line all the way to the engine, and turning over the engine from a cold start can't be exponentially more difficult then idling as to require 5 MINUTES worth of fuel.

    Considering how low the temperature gets in Winnipeg (-40), I think our frozen engines would use the most fuel to get up and running.

  6. As I understand it, leaving a vehicle's engine running when you're not in it is actually illegal in the UK. I recall that a few years back there were several cases of people in the US being run over when slamming their car boot shut. The car in question had a flaky automatic transmission and would occasionally jump into reverse when jolted. The news reports over here mentioned that such an accident would be unlikely in the UK since drivers aren't legally permited to leave the driving seat when the engine is running.

    But, while that's technically true, in practice people in the UK do leave cars running unattended. I suppose it's not a very safe thing to do, but we're not generally that safe road-users anyway. For example, parking on pavements, in no-stopping zones, on zig-zag-marked pedestrian-crossing areas, and on double-yellow lines is very common here, although all those practices are dangerous for pedestrians and other road users.

    It's not merely that we live on an overcrowded island either: people typically pull up on the pavement - say, beside a cash machine - when there's a legally marked-up parking place 20 yards down the road. It's sheer lack of concern for others. I have to say I've seen a great deterioration in public morals and manners over my own short lifetime in Britain, and I only hope most Americans are more public-spirited than many of us.

  7. My supra has that feature. It's called a Turbo Timer.

    I had to rewire my alarm to be able to activate while the car is running, but otherwise it works just like you say (variable time from 1 second to 9 minutes.)

  8. Last night Carey and I watched an international edition of "House Hunters." It featured some guy living with his girlfriend while looking for a small flat or home in the UK somewhere near her. The show explained that there are...

  9. In Siberia people often leave their cars running in a very cold weather (below -30ºC). First of all, because starting a car in this temperature could be quite tricky. Second, a nearly frozen oil is not the best lubricant on Earth.

  10. In extreme cold environments that fuel efficiency goes from like 1 minute to 15 minutes.

  11. Something similar came up at work today and I was about to use the 'Starting up uses 10 min of fuel" I'd heard as a kid then I googled and found this.

  12. I found this blogposting while doing a bit of research on laws and regulations on idling engines. Here in Norway there is a law against "idling your engine uneccessary", but because of the word "uneccessary", this law is for all practical purposes dead.

    The link mentioned by commenter Peter above no longer works. The correct link is:

    In my car's handbook (a Rover 75), it says that it is good fuel economy to turn off the engine if your stop is going to last more than 45 seconds.

    BTW, the above reference says the limit is 10 seconds.

  13. I'll tell you why it is illegal to leave your car running.
    We WALK to school !
    I have taught my kids to watch out for cars with engines running etc and work out if there is a driver in them before passing them. We have now to pass about 3 or 4 cars each day with engines running and no driver. I actually find it very uncomfortable because I have no idea if the person has left it in gear, handbrake on etc. One of these could easily slip off and the car lurch into us.
    I have also seen cars running with toddlers loose inside them and I am supposed to walk past ?!
    Also in addition it stinks to have to walk through the exhaust.
    So do not leave your engine running. Its also pathetic when people sit with their heaters on when it is not even cold outside.

  14. I live in a terrace house set close to the street and I hate it when thoughtless drivers sit in their cars outside my door with the motor running for long periods. Many of these people use their car as an office, making calls, entering data on a laptop, eating their lunch, etc. And all the time their motor is running, destroying the quiet and polluting the air all around them. When you complain after a proper period (ten minutes) they say they must run the motor for their heater, or their air conditioner, or their radio, even their bluetooth. These drivers don't care about anyone but themselves. There should be a law against this anti-social behaviour.