Switching off the engine in traffic - eco friendly?

I read in one of today's newspapers an article about making your driving more eco-friendly. One of the suggestions is to switch off the engine while held up in traffic.

I'm sure this is a great idea if the road is like a car park, but I also remember someone saying to me that it's only worth doing if you are stopped for at least a minute.

I was told it is because the surge of fuel required at startup outweighs that saved if the car is restarted in less than a minute.

What does anyone know about this? I'm sure it would be great to save some fuel during snarl-ups but are we doing more harm than good if we stop the engine for very short periods?

I remember getting a lift one time with a fella who used to do that, it was about 20 years ago now but always stuck in my mind, he wasn't being eco-friendly though, he was just broke and thought it saved petrol. Lovely bloke, he would have been an eco-warrior had the idea been invented then.

I think it is six of one alright, it is more eco-friendly to drive at lower revs though isn't it?

You will probably drain the battery aswell!

It only works if you are going to be stopped for a few minutes.

Wear and strain on electrical system and starter motor is increased.

I thought that switching off/on regularly in such situations used more fuel?

Exactly the point that was made to me about this practice - but there must come a point in any given queue of traffic when drivers will make a net saving of fuel by switching off the engine.

Does anyone know when exactly this is? I was told that the rule of thumb is that you must be able to leave the engine off for at least one minute - any less and it actually uses more fuel than it saved to restart the car.

at what point does the automatic engine stop take place in the BMWs mentioned above?

Whatever about the potential fuel savings, your starter motor will have a much reduced life. On the plus side, companies like Ford are hoping to have stop/start technology available for all their cars by 2010/11. I expect that folks will want or even expect this function in new cars by then.
Naturally, the more demand, the higher the volume produced , the cheaper the technology for everyone.

collis said:

Whatever about the potential fuel savings, your starter motor will have a much reduced life. On the plus side, companies like Ford are hoping to have stop/start technology available for all their cars by 2010/11. I expect that folks will want or even expect this function in new cars by then.
Naturally, the more demand, the higher the volume produced , the cheaper the technology for everyone.

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What he said, and in the meantime, those of you who want to save the planet, stop using your petrol-powered lawnmowers, chainsaws, brushcutters, etc. Unlike modern cars, they are currently exempt from emissions legislation.

To add to that list: BBQs and patio heaters

...and everything else that we use that contributes to the grand total of <1% of the CO2 the plant sucks up

I only turn off the engine at railway crossings where I know I could be sitting there for up to 3 or 4 mins. Not sure whether that's down to my inner eco-warrior or my bank balance!