Shutting off the engine at traffic lights (was-Want to Hypermile Please Help )
 

In the thread labeled "Want to Hypermile Please Help", the poster makes mention of turning off the engine at traffic lights. I do the same when I know I will be there for 1 minute or longer. The question is: when does it become economical to shut the engine off at traffic lights? I recall reading once that if you're stopped there for over a minute, then turn it off. I guess it matters what kind of vehicle you're driving too. Can anyone provide data that states if you know how long the light is, at what point it becomes a benefit / more economical to turn off the engine? We must remember that it takes more fuel to restart the vehicle.

I also wonder about the wear and tear on the starter by constantly shutting the engine off and restarting.

One thing about trying to get as much MPG out of your vehicle as possible, you also have to factor in wear costs. It’s like a previous post of mine that I mentioned how to drive down a mountain grade. I was taught (I use to drive a school bus) that I should stick the vehicle in the lowest gear possible, which would mean less use of the brakes. The comment was made, if you don’t, you’ll end up burning out your brakes and what will stop you then? So I was pretty much taught to use my transmission, because if that goes out, you’ll have your brakes to stop you. It’s somewhat the same about turning your engine off at lights. You end up putting more wear and tear on the starter.
So in conclusion, as I stated above, can anyone provide data about at what point it is more economical to shut your engine down at traffic lights if you know how long the light is?

Have a look in this thread:

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

I knew you would have the answer
 

I shut off my engine as much as possible when I'm not using it to drive the wheels.
I knew this info was out there, but I didn't know where, Thanx Metro.
Good article, well written and informative.
Covered all the questions I had before and while reading.
It should be a sticky and/or required reading.
S.

I wonder about starter wear also, fortunately both of my cars have very accessible starters and I can buy them used for ~$10 at the scrap yards.

Make sure voltage is high enough and there isn't excessive cranking. Aside from too much heat, a starter should last for hundreds of thousands of starts.

The only info I have on starter wear is that Wayne Gerdes replaced his on his accord after 80k or so miles. He is also pretty crazy when it comes to having the engine off, so that starter got a huge workout.

My X-Wife was a grinder in the morning, holding the key in start 8 - 10 seconds after thee car had started. Starters would get replaced every 11 - 12 months, irregardless of the car she had.
I bump the starter, release the key as soon as I hear rotation. My 1979 Rabbit had 230k on the clock with the OEM starter still bolted in when I sold it in 1992.
I believe it all depends on the hand turning the key.
Many new cars take you out of the equation now with starters run by the ECU that kick out the relay as soon as they see engine rotation above a preset limit. Hence all the button starts on high end cars. But even if you have a new Chevy truck you are not allowed to overrun the starter, the key just tells the ECU you want the car started. If you hold it too long the ECU still cuts power. If you don't hold it long enough the ECU keeps it turning.
I didn't mean to get so wordy, just wanted to voice my opinion,
Schultz

With my diesel and a working glow plug relay it takes two turns and it fires up. Recently the relay died and it takes about 10 seconds of cranking. I need a new relay.

Replacing a starter on the om617 is not fun, especially on the turbocharged model. I turn my car off when I have to wait for my turn to go when there is a one way road due to construction. I seem to catch lights at the right time.

Also, my engine doesn't consume that much fuel at idle.

Note that Gerdes' Accord was an automatic as well, so bump starting wasn't an option. But yes, you are right to point out there are few others as extreme when it comes to engine off.

Shultz: that's impresive. I owned 6 Rabbits - about one a year at the end of high school and through university - and replaced at least 3 VW starters, which suggests they weren't the most robust to start with. (Can't blame myself for the starter wear, since they were all well used when I got them!)

I loved that car, and regularly got >35 MPG.
I've been looking for another, that's why I got excited about the Scirocco down the street, that I can't afford, but it hasn't sold yet, so maybe I can afford it, but then my Wife would be mad 'cause there is another car in the driveway, but I could store it at my Friends Repair Shop, although I already have one there. so maybe it's not for me anyway.
Dang, I loved that car,
But I still think it is the operator who decides how long a starter will last. And previous owners are the worst abusers.;)
Yes, other factors play a role, but these factors can be controlled by the operator as well.
My second job as a Mechanic was at a VW Dealer, at one time I had 6 (six) Rabbits in the back yard. My house looked like a bad VW commercial.
Schultz.