Finances & Money Frugality

Save Money, Save Gas, Save Your Car’s Engine When Idling

This is a reprint of my original guest post at Budgets Are Sexy, with a few edits.

Prior to starting, I thought nothing of just letting the car idle when I was waiting outside of a store, parked in my driveway, or waiting to pick up my wife from work. But now that I’m focused on finance daily, either writing articles or working with our own money and budget, I look for ways to save money in the most common and uncommon ways. Well, this is one of those common, and common sense, ways to save money.

When I walk through the parking lot now, and see a car just sitting there idling (i.e. the engine is running for no reason), I just want to walk up, knock on the window and ask the driver (or passenger) why they’re doing it. I’ve refrained from doing so thus far only out of fear of getting mistaken as a carjacker and shot. So instead, I’m spreading the word here in hopes that at least one person turns off the car when idling. Not only will you save money and gas, but depending on how long you’re idling, you’ll save a bit of wear on your engine. And don’t chime in about the wear-and-tear on your starter; it’ll survive just fine.

Update: The rule of thumb is to shut off your engine if you know you’ll be idling for over 30 seconds. It’s not a firm number, just an advised threshold. Also, the argument that your car wastes more gas starting up only applies to older cars that use a carburator. Newer fuel-injected cars manage fuel during startup differently.

Update: I also found this interesting worksheet to calculate idling costs. I’m not sure how they came up with the usage numbers when idling (see table at end of PDF), but it’ll at least give you an approximate cost figure.

You don’t need to limit the times you shut off the engine to just when you’re outside the store or your home. Now, at traffic signals with which I’m familiar, I stick my truck in neutral and shut off the engine. The only reason I don’t throw it into park is because all my doors automatically unlock and I’d rather keep them locked for my protection.

Update: Some people have said shutting off your engine while in traffic is illegal in some states, and you can be ticketed. I searched but couldn’t find anything official, so if you know of states who will fine you for shutting off your vehicle while sitting at a light (I don’t mean while on the highway in bumper-to-bumper traffic), then please post the link to the applicable state law.

At the traffic light near my home, if I get the red light, I know I have at least 45 seconds of idling so shutting off the engine for that time is definitely worth it. I know when to start up the truck again by watching the pedestrian crossing signals and when they start flashing red. Some signals even give you a countdown which helps your timing even more.

The Safety Factor

There only one main argument against shutting off your vehicle while on the roadway: getting out of the way of emergency vehicles (or just getting out of the way). But here’s the thing; you have more than enough time from hearing the sirens to turning on your engine and moving. Personally, I’ve never been caught in this situation, but I have forgotten the truck was off once or twice and it was only a split second to start up and get moving. But check with your state and local laws to ensure you’re not breaking the law.

Getting Your Stuff Done BEFORE Starting Up

Lastly, how many times do you start up the car, then buckle up, then situate your cup of coffee, then adjust the mirrors, then plug in your phone to the charger, then blah blah blah. How about you take care of everything else BEFORE starting the car? All those seconds add up and keep in mind that it’s not just about saving money, it’s also about not wasting. I recall in driver’s education that you’re supposed to buckle-up before you start the car anyway. They dinged you on your test if you didn’t.

So overall, if you aren’t comfortable with turning off your car while stopped at a red light, I hope at least you’ll shut it off when you’re just idling in the parking lot or driveway.

Photo by Dr Keats

About the author

Clever Dude


  • It’s not just to get out of the way of emergency vehicles, you should never turn off your engine while on the roadway because sometimes other drivers aren’t prepared to stop (read: aren’t paying attention) and for your own safety you need to be able to maneuver out of the way. Turn off your car while going into the store, or waiting in your driveway, or even in a fast food drive-thru line, but for goodness’ sake please keep your car running while on the road.

  • M, yes I have been rear-ended, specifically on the beltway here in D.C. However, having my car running or not would have no impact on whether someone else wasn’t paying attention. I had my car running, but I had nowhere to go and no time to know to move anyway.

  • I blogged about idling this morning, too. That worksheet is really helpful! I think I’ll figure out our car’s exact idling waste with it.

  • Not that I agree, but some people have their cars idling, say, while waiting for someone, to run the air conditioning, without running down the battery. Don’t know if it makes sense, but there has been that argument.

  • Turning off the car, while driving is taking saving money on gas to the extremes. However, if it’s saving gas, it’s saving gas. As for me? I converted my car to run off waste veggie oil. It’s totally great for my wallet.

  • @Austin, you think this is extreme? How about trying to take a highway ramp at full speed so you can use your momentum to keep you from having to use the gas once you get off the exit? Or how about tailgating a tractor-trailer?

    Mimicking a hybrid vehicle is far from extreme.

  • Austin –

    How do you modify your engine to burn waste vegetable oil? I drive a Chevy Blazer that uses regular gas – how do I fill it up with waste oil instead? Where do you get the waste oil from?

  • @Susan, you need an old diesel engine vehicle. A regular gasoline engine won’t work (i.e. your blazer), and many newer diesels won’t work either because they can’t handle the harshness of the biodiesel fuel. I suggest that you google “biodiesel” to learn more.

  • Well, that doesn’t help me at all 🙂 What else can I get my gasoline powered car to run on? I’m going to have to switch to a Smartcar and say a prayer every time I get behind the wheel that I don’t get hit by a landscaping truck (which is why I stopped driving little cars in the 1st place).

  • I see this advice as “penny wise, pound foolish”.

    “And don’t chime in about the wear-and-tear on your starter; it’ll survive just fine.” Are you sure? Will you batteries and alternator survive just fine as well? The savings from shutting off the engine at a stoplight is beyond miniscule. The cost of a new battery and alternator is substantial.

    My car uses about 0.2 gallons per hour while idling. That means that idling for an *hour* costs me about $0.80. Idling for a minute at a stoplight costs me about $0.01. Replacing my battery and alternator costs me about $300.

    My truck uses about 0.3 gallons per hour while idling. That means that idling my truck for an hour costs me about $1.20. Idling for a minute at a stoplight costs me about $.02. Replacing both batteries and the alternator costs about $650.

    I completely agree that idling for an hour is wasteful, but turning off your engine at a stoplight is foolish. Hybrids have special starters and very small gas engines that are very easy to start. Not true for non-hybrids, and especially not true for larger trucks. Starting a vehicle drains quite a bit of energy from the batteries.

  • Actually all public buses in Tokyo are required to shut off their engines instead of idling. This helps stop pollution and their mass transit is far superior. So you may be on to something.


  • @Donald, first, you should probably lay off the CAPS LOCK. I know it makes grammar a bit easier, but it looks like you’re yelling.

    Anyway, to your first comment, no, I wouldn’t try a gimmick unless it was permitted under my car’s warranty. If my car was out of warranty, I probably still wouldn’t try bolt-ons or fuel additives unless the auto industry (actual manufacturers) stood by the claims as well. That is, if Honda’s actual spokesperson said “this thing works and is OK for your Honda”.

  • Could you please send me link to the chart on figuring out idling and the cost of gas. I do not see it as instructed at the end of the PDF. I have a Mac and sometimes things do ot translate the same as on PCs. I am trying to get my employer to pay me and others for using our cars as security and sitting in parking lots with our cars idling. Thank you.

  • I’ve been turning off my engine for a few months now, while sitting at a drive through at the bank etc. Often wondered if starting the car back up wasted more gas. Now I know and thanks for the info—I will continue turing off my car. If someone behind me gets impatient while I start up—OH WELL, get over it.

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