Turning the car off at stop lights (questions about when, how long & wear issues)

[NoCO2]

I have read that in some parts of the world, I believe Germany was the place specifically, the law is that you must shut off your car at stop lights in which you are at a stand still for more then 30 seconds. I know some people here do it as well and I have done this a few times myself while sitting at a light for a long time. I was just wondering, for anyone here who does it. How do you tell when to start your engine back up? I try to look at the other lights, but sometimes I just can't see them so that method is unreliable. The other question is, at what point do you see it a good idea to kill the engine? Do you wait 10 seconds, 30 seconds? Do you do it as you approach the light?

I'm just wondering because I'm always worried that when I do this I'm going to mis-read something I'm seeing with the light queuing and that it will go green and my engine will still be off. It's not that big of a deal because my car tends to start up almost instantly after I hit the key, but I just don't like feeling as if my efforts to save fuel is holding others up from doing what they need to do. (That reverse drafting thing is absolutely perfect for my situation)

[DifferentPointofView]

I usually don't shut mine off because stop lights usually turn green by the time I shut it off anyway, and shutting off and restarting you engine uses the same amount of fuel that it would idling for 30 seconds, so unless your wait is longer, you don't benefit, and you wear out your starter faster. If I have to use a drive-thru, I shut off the engine and use the hand brake because it's downhill to the window, and I can neutral coast there, and I usually wait way more than a minute. My brother thinks it a retarded Idea, but I think he's the retarded one. Why use gas when you could use the force of gravity to make you go infinite mpg?

[NoCO2]

Yea, the only concern I have is the starter problem. I can only imagine the cost of having to replace that every few years or so from excessive use.

[basjoos]

If you are at the front of the line next to the intersection, you can often see the lights for the cross traffic, so when you see it go to yellow, start your engine. At night, it is very easy to see the color of the cross traffic lights. If you are several cars back in line, it is easy enough to start your car as soon as the light turns green and have it up and running by the time the car ahead of you starts moving. If the opposing traffic and its left turn lane get the green light before you do, you'll need to get familiar the timing of that traffic signal to know how long the left turn lane light remains green once it has cleared of traffic and so when to expect your light to go green.

[AndrewJ]

I just start the car when the light turns green. I was initially concerned about holding up traffic, but after doing it that way for 2 months or so I haven't been honked at once. In fact, I'm usually pulling away as most of the people driving automatics who are idling the whole time.

[cfg83]

Hello -

I mostly do strategic on/off. If I don't know the area and/or the timing of the light, I will probably leave the car on. If I am 5+ cars back and I can see my signal, the time it takes other cars to start moving can be enough for me to restart the car. Other times I can use the left-turn signal as my green for starting the car.

I have all sorts of dos and don'ts for this that are context driven,

CarloSW2

[MetroMPG]

Originally Posted by DifferentPointofView

shutting off and restarting you engine uses the same amount of fuel that it would idling for 30 seconds, so unless your wait is longer, you don't benefit

That's just not true.

It may have been true years ago before computer control & fuel injection.

See this thread, where it was concluded that...

"the additional fuel consumed by restarting your engine is equivalent to about 0.2 seconds of idling. So you don't even need to consider how long you might be stopping for. If you're interested in reducing fuel consumption, turn your engine off whenever you can."

Source: How much fuel does it take to re-start a warm engine?

You're potentially right about starter wear however. Yes, it will wear more. Enough to be a problem? I doubt it, but can't offer anything more than my opinion on that issue.

[DifferentPointofView]

I'm just going off of my big 'ol 4.0L which dumps a bunch of fuel to start the thing back up. When I start up my Jeep enough times in a row, the fuel guage starts to drop like a rock. I can easily use 1/8 tank from doing that. That's like 75 miles I could have gone wasted. I don't know how exactly how my engine works. But according to Jeep's website, if your going to be idling for more than a minute, shut it off, because you will be using more fuel than if you shut it off and turned it back on.

On more modern vehicles, I could see this. I could definitely see this in my moms Caliber. But what I don't see is how when you crank the engine how it could only add up to .2 seconds of idling. it revs up to almost twice Idle, dumps in fuel in the time the vehicle is cranking, and you're stopped at the light even still, and if you throw it in gear while the rpms are up, you jerk forward and cause odd transmission jerkyness. I could see 5-10 seconds, but not that small of an amount.

[Frank Lee]

As far as starter wear goes, this past year I've replaced brush sets on two starters for my vehicles. These starters are 13 and 15 years old, and have never been serviced before. Everything but the brushes was just fine- didn't even need to turn the commutators. One set of brushes cost $6; the other $13.

[Lazarus]

Originally Posted by Frank Lee

As far as starter wear goes, this past year I've replaced brush sets on two starters for my vehicles. These starters are 13 and 15 years old, and have never been serviced before. Everything but the brushes was just fine- didn't even need to turn the commutators. One set of brushes cost $6; the other $13.

I agree. I can't remember the last time I had to replace a starter and I keep cars in the 150-200k range. Unless you're cranking it 30 seconds at a time to get it going I don't think that is much of an issue.