I'm told that in New Jersey, you'll get a nice big fine if you leave your car idling and unattended. It's probably because too many cars are stolen -- maybe we shou...nah. :)

Here are some answers to that question http://answers.google.com/answers/threadview?id=428015
It seems that car technology has come a long way, but no one seems to have told anyone about it, a lot of people I've talked to about this really have no clue about how their brand new trucks work. A landscaper I once worked for told me he drove home one night and went to bed, when he woke up the next morning his F350 was still idling in the driveway. "It's good for them," he said, "It hurts the engine to turn it on and off a lot."
I've read that 10 seconds of idling uses more fuel than restarting your car!

This idling urban legend arose in the days when ignitions were manual and fuel mixures relied on carburators, not computer monitored injectors. I'm guessing people use the sun's heat as a rationale in the middle of summer but when the weather is nice its really silly.

With the price of gas the way it is, I've taken a guerilla approach to saving gas....

Not that I'm condoning this activity, but its something I do now with a little more frequency.

If I'm at an intersection, and I can cut through a parking lot / gas station, then I'll do it.

I don't speed through or do so in a manner that would pose a safety issue, but I do this only when I'm familiar with the intersection and can gurantee a quick, time and gas saving manuever.

Eventually, I'll have a Tango and won't worry about such idle issues when driving around town.

Don't you people know that trees are a renewable resource. All you have to do is plant a sapling and in time you've got a full grown tree.
If you ask me there are too many trees already. And trees pollute the air with a lot of Carbon Dioxide.
"Down with trees"

On my commute there are two very long lights I'm often stuck at. From the approach you can clearly see the opposing traffic lights. So I turn off my engine when I'm stopped at these lights and turn it back on when the opposing light turns yellow. I was worried I was damaging my engine or wasting gas by doing this, so thanks for the reassurance!

David, did you work for the Reagan administration? What you say sounds familiar...

Nonny, there are many countries where basically everyone shuts off their engines at traffic lights.

Hybrid cars do it automatically, but some cars are starting to have the feature without the rest of the hybrid package. I've read about a version of the Toyota Yaris that shuts off the engine in some conditions, and the engine restarts instantly when you take your foot off the brake pedal.

All the car needs to do that is a bigger starter and alternator, I think.

I think the idling phenomenon is especially big with contractors. I had a friend who was building a home and at one point had three contractors working for him who would come over and park in the middle of the driveway, totally blocking it to anyone else, and letting their enormous heavy-duty pickups idle for a half hour or more.

Well cutting through parking lots are not only illegal and dangerous, it is asking for road rage from the Yahoo that watches you do it. Now - if everyone would to cut through the parking lot - staying at the light would be the quicker method.

I think there are more logical, legal, safe, less annoying ways to save gas...

When it's cold, letting the car defrost while idling (and while digging it out of the snow and scraping off the external ice) is more attractive. 30 seconds to a minute might be fine for the engines of modern cars, but the internal defrost and temperature are not so quick to change.

I don't actually understand why somebody would idle a car unattended, though.

Jim, unless you are letting the car heat up while you are inside the house (which is another problem, because people tend to forget their cars and let them idle longer than they would if they had been inside), there is no difference between letting the car heat up for longer than a minute while parked and letting the car heat up while driving... Except maybe that the car will heat up faster with driving (not hard highway driving, mind you).

Seems like fleet drivers and diesel truck drivers of all sizes are willing to let their trucks idle rather than turn them off. As a former diesel mechanic, I can't see the point. Many rig drivers keep their engines on while they are sleeping to keep the heat or AC on. Trailers with sleeper cabs should have an external power hookup to deal with this.
Also there are the folks who leave their car on for fear that it will not start again once turned off. This is sad.
My suggestion for idling trucks and cars that are left with no occupants is to reach in and shut them off. People ask me why I turned their car off, and I ask them why they left it on. Most of the time I get 'Because I wanted to', which is just dumb.

Yes a car will warm up faster if you drive it rather than just let it idle. As you say, let it get some heat into it before hitting the highway. I'd look for auto shut off to become common.

I saw a system made by Visteon an automotive supply company that is a motor/alternator. You stop at a light the engine stops turning but the belt doesn't as the alternator is now a motor (keeps the AC running etc). The crank pully is controled by an electromagnetic clutch and freewheels when the engine is stopped. When it's time to go the clutch is engaged and the the engine is started by the belt.

Tim,

I had a quick look at visteon websites but couldn't find what you're talking about. Let me know if you have a URL.

One thing that didn't seem to get mentioned here, is why idling is WORSE than driving. When you drive your car, the emissions controls that remove large amounts of pollution from your engine are also running. But when you stop and idle, your car instantly turns off all controls, to prevent the car from stalling. Hybrids shut of their engine every time you stop, which is why they have such low emissions (which is the true benefit of hybrids, not the gas mileage)




I've read that some truckstops are offering AC/heat and electricity to drivers who sleep in their trucks, so that they can turn off their engines and save fuel. This would greatly reduce pollution in America, seeing as trucks have little or no emissions control (the real reason why SUV's suck).

there is no difference between letting the car heat up for longer than a minute while parked and letting the car heat up while driving...

MGR, you've obviously never left your car outside on a night when it's -20 C and then tried to drive it; you have to let it idle for a while until the windshield is warm enough that you don't have frost forming on it, otherwise you can't see where you're driving!

Chris,

I live in Canada and I've driven in -40 celcius weather, so I know what you are talking about.

My comments always assume that the readers are reasonable and will adapt my tips to their particular context. Since most Treehugger readers are from the US, I skipped the heavy snow section - but it's pretty safe to assume that anyone who lives in a place where there's lots of snow already knows about that.

But I'd add that even in -20, if there is no ice and snow on your car, you can usually start driving (not hard, but driving) as soon, after a minute or two as your visibility is good. Don't need to wait 20 minutes until the car is toasty inside, as I see many people do.

I've been trying to leave the car on or leave someone in the car while I run in places because I heard on the radio once that you put out the most pollution right when you start the engine :( I suck

Don't worry about it, anonymous. I'm sure your intentions were good. At least now you've learned something new.

As for the wrose emissions when you start the car, it's partly true; worse emissions come from when the catalytic converter is cold. But after it's warm, it takes a while to cool down and shutting down the car for even many minutes won't pose a problem.

As for letting it idle for a long time before starting to drive, the catalytic converter while warm up faster if you start to drive soon after turning on the engine anyway...

found some useful links to conserving gasoline through the addition of a bit of acetone to your tank:

http://www.freerepublic.com/focus/f-news/1450915/posts

http://www.industrialnewsupdate.com/news/oil-energy/archives/oil_energy_prices/index.php

http://peswiki.com/index.php/Directory:Acetone_as_a_Fuel_Additive

Many contractors will purchase and install inverters for their rigs. Usually for the inverter to work you need to leave the engine running.

I do not know if using your vehicle's engine to run an inverter is more treehugger than buying and maintaining an entire 'nother engine in the form of a "generator".

Similarily I think some truck drivers like to watch TV, surf the web, and maintain radio contact with the home office. All of that electrical infrastructure usually runs off of an inverter as well.

I think they also like to leave some running lights on at night so they don't get crashed into by inattentive 4-wheelers.

I shift to N at red lights. Do you car buffs know if it's bad for the transmission to be shifted back and forth like that?

Nikki,

You're just adding wear to your transmission, with no eco-benefit. But if your car is a standard/stick, then shifting into neutral at a long light will actually reduce wear on your clutch plate. The hundreds of $ you'll save on replacing that could be donated to an 'eco-profit' organization ;)

Nikki, I've heard about that as well--if you have an automatic and you're in gear, your engine is constantly trying to move, even when you're stopped at a light. Putting it into neutral at lights will at least save your engine some wear, but I don't know about the emissions part of it.

Delphi has systems for OEM suppliers that allow the engine to stop at idle. I am not in that division, but I think a few trucks out there have the systems. It restarts the vehicle within 200 mS of pressing the gas pedal.

The systems that I saw at our technology show worked in two ways.

1) The alternator (and starter) is replaced with a combination starter/alternator. It restarts the vehicle using the belt system.

2) The system is actually in-line with the engine and transmission. It does the same as #1.

Here are two links:

http://delphi.com/news/pressReleases/pr15473-10232002
http://delphi.com/pdf/techpapers/2004-01-0566.pdf

i used to not idle before i had kids, but now i find myself doing it all the time to keep them from getting too hot or too cold while we wait in the car for whatever reason. sometimes it just doesn't seem worth getting two kids out of carseats, into a climate-controlled building and then buckled back into carseats...especially if one or both are asleep. modern life, eh? i don't think cavepeople worried about this!

if the weather is mild enough i'll turn off the engine until we get uncomfortable, then turn it back on to get back to comfortable, then turn off the engine again, but i'm never sure if this is worse than leaving the engine on and maintaining a constant temp.