Turning the engine off in traffic?

[akkord]

if waiting for long periods of time (5+ minutes etc)...is it doing more harm than good? is it saving petrol?

should this be done?

[Ved]

I do it if there is clearly nothing happening in front. Starting the car does use a blip more petrol per second than just running but you will save petrol rather than just having it on. It'll do no harm to your car at all unless the starter motor and injectors are crap anyway.

[akkord]

my thoughts too...i ask as i've heard mixed things about doing this.

cheers for the reply.

[davepoth]

Here's what the Canadian Government has to say:

http://oee.nrcan.gc.ca/transportation/idling/why-i...

Any more than 10 seconds at idle and it is a good idea to switch off. I wouldn't do it that much in my car, but solely because it would cause excess wear on the starter on my stupid drive to work.

[911p]

It must save fuel considering that many new cars have stop-start.

[kambites]

I seem to remember reading somewhere that starting warm engine uses about the same amount of energy as ten seconds of idling, or there abouts. Might have been complete rubbish though.

[Aviz]

Can't wait till all these stop start enabled cars get a bit older. Lines of traffic all struggling to start every 5 minutes

[edo]

IIRC correctly, anything more than about 20 secs is worth it.

[thinfourth2]

I also find the second that i switch the engine off the traffic infront starts to move

[PintOfKittens]

thinfourth2 said:

I also find the second that i switch the engine off the traffic infront starts to move

I have that power too, along with as soon as I put the handbrake on, the traffic light that's been on red for a millenium instantly changes.

[Graebob]

PintOfKittens said:

thinfourth2 said:

I also find the second that i switch the engine off the traffic infront starts to move

I have that power too, along with as soon as I put the handbrake on, the traffic light that's been on red for a millenium instantly changes.

Put it on earlier then, you're holding the rest of us up! Silly sod

Edited by Graebob on Tuesday 22 June 08:44

[kambites]

Aviz said:

Can't wait till all these stop start enabled cars get a bit older. Lines of traffic all struggling to start every 5 minutes

The systems test that the battery has enough charge to restart the engine and that the engine is up to temperature before allowing it to shut down, so that really shouldn't happen.

[Dracoro]

I would avoid if car battery is weak or car has general warm starting problems (not so much a problem these days but old cars may have trouble).

[kambites]

Dracoro said:

I would avoid if car battery is weak or car has general warm starting problems (not so much a problem these days but old cars may have trouble).

Unfortunately those old cars with weak batteries are also the ones that tend to overheat in traffic, so you have to switch them off.

[bigdods]

Just did some quick calculations, based on the fuel computer which is actually quite accurate in my car (Omega 3.0 V6)

Idling, Aircon off: 1.36 Litres/hour = £1.62 = 2.7p per minute

Idling, Aircon on: 1.82 Litrs/Hour = £2.16 = 3.6p per minute

To be honest , I'd rather run the engine and have the aircon on at those costs. And of course if you have a smaller engine or diesel I'm sure those costs are a lot lower.

[Tom74]

911p said:

It must save fuel considering that many new cars have stop-start.

Drove the wifes car in to work today which has stop start, I don't think it saves fuel as much as you don't use fuel when the car is stationery, hence increasing the MPG figure (unless you are stopped for a while) if that makes sense?

[Kevin VRs]

Tom74 said:

Drove the wifes car in to work today which has stop start, I don't think it saves fuel as much as you don't use fuel when the car is stationery, hence increasing the MPG figure (unless you are stopped for a while) if that makes sense?

That does not make sense. It can only increase the average mpg by saving fuel. If the engine is off then it is using no fuel, when running it is. I always turn off the engine at level crossings and at traffic lights with a long cycle time (20 secs +) and it does save fuel.

[Snoop Bagg]

My Cooper S automatically turns the engine off at the lights which is pretty good. It seems to do much more mpg than my previous Cooper S on an 04 plate so IMO it's a great thing and the performance is also much better.

When you stop and take it out of gear and your foot off the clutch it cuts off and then when you put your foot on the clutch again to move off it automatically starts again.

The only niggle is that I'm sure when you pull up next to someone at the lights some people either think you've stalled it or are one of those eco-mentalist's!

[rev-erend]

It's a good idea if idle for more than 10~30 seconds.. but be careful
in the winter time as lights and rear screen heaters etc take it out
of the battery and repeated restarting of the engine could see you calling
the AA / RAC if you are unlucky.

If on days like today - you will loose the air con .. too hot already.

[Deva Link]

BMW say their stop/start saves fuel after 2 seconds.

I drove a Merc B Class with stop/start a while ago and it was surprising transparent to use. I did everything in just the same way and ws barely aware of the engine stopping and restarting, although the Merc system has a belt driven 24V starter/alternator, so it's not the same noise on restarting as a normal starter.

They don't work if it's too hot/cold/battery low etc.