Is it better to keep your car running when you stop for a short time or kill the engine?

Question

In my job I often have to stop my car, get out and hammer a sign into the ground early on a Saturday morning (as a real estate agent). Now its early and safe so there is no fear of my car getting stolen. My question is- is it more fuel efficent to keep my car running through out this process or shut it down and start it up again. I've heard starting up your car consumes more fuel. Whats the right answer? Is there a certain time you leave it running that is equal to shutting it down and starting it up again?

Answer 1

Its better to leave the car engine off. Its just a myth that its better to leave the car running, and false, because the electrical starter motor actually starts your car (though very briefly) and your car will already be warmed up and the gasoline vaporizing normally.

That 500-1000RPM (just guessing) or so you see at idle is to prevent the engine from stalling, and at every crank its injecting more fuel. If you just leave your car on it'll only burn more gas =].

Answer 2

Any fuel you don't burn is more efficient.  But it's safer to turn off your engine.  I know it sounds silly, but people  have jumped out of their car while it was idling and forgot to put it in park or set the brake.  It only takes once to understand how dangerous it is to leave your car running when nobody is behind the wheel.  Watching your empty car roll away and crash into someone's car or home is an awfully sick feeling...

Restarting a warm engine doesn't take lots of fuel.  That's a myth.  Your starter and battery also won't wear out appreciably faster.  I've driven vehicles over 200K miles and had both the original battery and starter.  What will age your car is stopping for a couple minutes and all the oil draining down, then restarting an essentially "dry" engine.  Service your car acording to the severe maintenance schedule.  Get a high quality oil, preferably a synthetic, since it will adhere to parts better for restarts.  It's a business expense and your car is critical to your business, so take good care of it.

Best of both worlds?  A hybrid engine won't run when you're stopped, only when it's necessary to supplement the electrical motors and batteries.  Turning the ignition only energizes the electric components.  The constant stopping will serve to recharge the batteries, too.  I'm not a greenie, but this is a case where it makes sense.  My driving style doesn't warrant hybrids (lots of contant highway miles) and I can't stand them, to boot, but it sounds like you'd benefit from one.  Lexus makes some hybrids any agent can be proud to drive...

Speaking of China, here's a Chinese proverb for the "leave it running, you're not hurting the environment" responder... "A journey of a thousand miles begins with one step..."

Answer 3

Stop the engine .You will save fuel.You will save the environment.You will increase the life span of your motor.

Answer 4

If it has to idle more than 1 min., shut her down, the number 1 way that people get their car stolen, is to leave it running, and go into a store, they come out to no car and saying "I was only in the store for a minute", it only takes a few seconds to jump in and take off, leaving YOU holding the bag (Literally) ! If it's early AM, that makes it even easier.

Answer 5

Look at it THIS way:

Maybe you'll save a little gas by shutting it down and re-starting it constantly, but the battery and starter will have to be replaced sooner.

I figure: it's easier to replace a little gas than a starter and battery.

And the carbon monoxide? just about every other country in the world pays NO attention to emissions, so your one little car compared to a billion others in China........no biggie

Answer 6

Starting your car uses alot of fuel, general rule of thumb I use if it's less then 5 minutes and you don't have to worry about it getting stolen just leave it running, and don't lock your doors.

Answer 7

Leave it running. You will be better off. By leaving it running, you are reducing stress on the battery and starter. Since your next to it and it is early nobody is going to take it(like you said). Plus you are wasting time by turning it off and restarting the car versus letting it idle.

The fuel cost difference is virtually nothing, as well as the difference in emissions!!!

Answer 8

Because every bit of carbon monoxide exhause from cars is dangerous for people, plants, pets and our drinking, water and possibly global warming, it is always better to turn your car off whenever you are not driving it.  So many children have asthma now, and car emissions affect that.  Please don't leave it running while you do that.  Thanks.  Jay