I have a Greenline II with the Start/Stop system. I was reading my handbook and in the back the 'Driving and the Environment' section had this to say under the 'Reducing idling' heading:

"It is worthwhile switching off the engine in a traffic jam or when waiting at a level crossing or at traffic lights with a lengthy red phase. Even after just 30 - 40 seconds you will have saved more fuel than that is needed when you start the engine up again."

So now I'm a bit confused frankly.

If the Start/Stop system switches my engine off for, say, just 15 secs - then overall does that mean more fuel has been used compared to having just left the engine running?

I regularly find myself in Start/Stop traffic when commuting to work. It's a long commute taking just under two hours.

However, most typically, I'm stopped for 10-15 secs before being able to shift forward a short way again. Not the 30-40secs or longer described by the handbook.

So then... in such circumstances of stopping regularly for 10-15 secs, is the Stop/Start system actually causing me to use more fuel than if the engine had been left running??

Edited 15 August, 201213 yr by Jules Tohpipi

I've seen so many numbers banded around the internet with regards to this.

Personally, I think as long as you're going to be at the lights longer than about 7 seconds, it'll be fine. I've noticed the average consumption going down every 7 or so seconds when sat with the engine one, and it doesn't change with start/stop.

To save fuel, have the engine running as little as possible and with your foot on the accelerator as little as possible. So try and coast (the greenline does this very well) and when you come to a stop and you can see you'll be there at least 10 seconds, let the start/stop do its work.

I know some people turn it off but I don't know why. Its brilliant, helps your wallet, helps the environment and is a win/win situation.

Where do you get your data from regarding 10 seconds for the Start/Stop?

You can see it on the cars mpg gauge and I do the same journey many times a week to work at back getting quite consistent results. If the engine is left running in slow traffic, the car does far worse than when the engine is just off and then back on to carry on the journey. I hit a peak of 86mpg last week travelling to work (7.5 miles) which included one point when the engine turned itself off at a traffic light.

I wonder if the reported fuel savings outweigh the extra wear on the starter motor, flywheel ring gear and battery? Too early to tell, I suppose.

Ray

good point Ray have all these parts been up graded to with stand the extra use would be interesting to find out.or does the car industry not want us to find out.could be a nice Little extra profit in a few years time for them all the 4-5 year old car with the parts needing to be replaced??

bill

From an emissions point of view at least, it's better. Old parts could be recycled, extra burnt fuel goes straight into the atmosphere.

But then manufacturing replacement parts causes emissions too so it's by no means clear cut.

bmw have been running this for year, my mate brought my old car and no issues after 4 years.

Sent from my GT-I9300 using Tapatalk 2

I doubt the battery needs to be upgraded, they're pretty good these days.

With regards to start/stop, some cars have an upgraded starter motor, and other cars actually have two starter motors, one for the stop/stop and one for normal starting and stopping the engine.

That is exactly what I have been thinking Argee. My car shows fuel consumption of about 1.7L/hr when idling at the lights and I have always wondered how stop/start can improve fuel consumption by the percentages they are (quoted as) delivering. The extra wear and tear on the entire running gear must increase plus, if on variable servicing, doesn't this then give you hundreds of extra stop/start cycles and so decrease service intervals? I have to admit not knowing a lot about it as I don't have it and don't need it because I live in an area with very little traffic and few traffic lights/stop signs.