Why does the 135i burn 39.5L/100KM petrol at idle, 0.0L/100KM while coasting?

[fatjoez]

you guys need to reverse your fuel meter in the car settings

put it on how many litres are being used per 100mile or km or something

Then you'll see how much fuel is actually being consumed
Personally I think 0.00Litres per 100km is nicer way to measure your performance than saying I'm getting 99.9miles per gallon

& syenisch i think you're right personally, I've found that I can get down a certain hill near my house all the way to a roundabout on idle, but in gear I can't make it without having to accelerate the last 3/4

wonder which uses less fuel..

hmmm

[Jeef Beef]

Originally Posted by fatjoez

you guys need to reverse your fuel meter in the car settings

put it on how many litres are being used per 100mile or km or something

Then you'll see how much fuel is actually being consumed
Personally I think 0.00Litres per 100km is nicer way to measure your performance than saying I'm getting 99.9miles per gallon

& syenisch i think you're right personally, I've found that I can get down a certain hill near my house all the way to a roundabout on idle, but in gear I can't make it without having to accelerate the last 3/4

wonder which uses less fuel..

hmmm

Uhm MPG is the standard measure of fuel consumption in the US so I don't think it's fair to tell them to change their unit of measurement to L/100km. Both do the same thing and give a figure that you can compare to other cars.

If you want maximum momentum down the gradient then going in neutral would be the best - the meagre amount of fuel burned at keeping the car idling will be offset by the extra speed.

However, looking at it from a safety (and law abiding) perspective, keeping your car in gear at all times is the best option. Coasting in neutral can be very dangerous when there is a sudden need to accelerate - your engine is not connected to your wheels and you need to throttle blip, flick it into gear before you have any power.

Choosing the correct gear (i.e. 3rd for a steep hill) can provide adequate engine braking to keep you on the speed limit without having to ride your brakes.

[fatjoez]

Okay so can someone set the record straight, how much fuel is consumed at idle stopped at a traffic light

[jeremyc74]

Originally Posted by fatjoez

Okay so can someone set the record straight, how much fuel is consumed at idle stopped at a traffic light

It's going to vary depending on A/C use, headlights, temperature, ect.

My previous car would switch to gallons (or liters) per hour when you were sitting still. It would bounce between .5 and .6 gallons/hour IIRC, but that was a 6.0L V8. I would imagine the N54 is considerably less than that with its smaller displacement and the DI.

You could always fill it up, let it idle for a couple of hours, then top it off again if you want a better idea.

[MOCKBA]

I can tell that N54 engine is very economical at addle. It happens that I forgot to turn engine off when arrived at work, so when I went for lunch, after 3 hours, I noticed my engine is still running. So finally when I did refill I noticed that distance between refills reduced only by 15 miles, so engine take fuel for 15 miles the same as for 3 hours idling. I hope it makes sense.

[Beemer323]

Originally Posted by syenisch

You're still better off coasting out of hear in most cases because you can coast so much FURTHER before slowing down than coasting in gear. Often times if I see a distant red light I will coast in neutral and then if I need to come to a stop or slow down significantly I will throw it in to gear. I have found that if I coast in gear I will unnecessarily slow down more than I need to, and then have to speed up again to get to the speed limit. Save a little fuel when coasting but use a lot more to speed back up. Bad!

Its all very simple. Coast down a hill in 5th so you loose less speed and the engine is still turning over higher than idle so you dont use fuel. If you have cruise control on, switch it off to maintain the correct speed through slight engine braking and then you can resume if the speed drops lower than needed.