how much fuel used in idle mode

mutley74

How much fuel does a diesel 1.6 engine use when idling at lights etc? (without air con and rear heaters on)

as I got a new car with a stop start and interested how much it can save me longer term...

yangptangkipperbang

mutley74 wrote: »

How much fuel does a diesel 1.6 engine use when idling at lights etc? (without air con and rear heaters on)

Not as much as the car dealer would lead you to believe !

If you read up on this subject you will find claims of fuel savings of up to 14% being claimed for stop/start systems.
1. This is quite feasible if you spend all your time driving in a large city with lots of lights and lots of stop/start traffic.
2. This is pie in the sky if you spend all your time driving in a relatively light free area with free flowing traffic.

To set against any fuel saving is increased wear on your car's starting system.............

..........you pays your money....

WTFH

It depends how often you are stopped at lights. If you are driving in a town, it will save you money over time, but if you only have one set of lights per day, you'll not notice it.

It also depends on how well the stop start is implemented, so make & model would help.

And in a modern car (contrary to what some older opinions may be) it's better to leave the climate control on auto at a set temperature (say 18c) all the time, rather than using just AC or switching it off and on, and it's generally more efficient than having the windows down when it's warm.

Ultrasonic

To give you a ball park figure, IIRC my 2005 1.9 TDi uses about 0.14 gallons per hour at idle when warmed up. (Figure from a Scangauge II.)

Ultrasonic

WTFH wrote: »

And in a modern car (contrary to what some older opinions may be) it's better to leave the climate control on auto at a set temperature (say 18c) all the time, rather than using just AC or switching it off and on, and it's generally more efficient than having the windows down when it's warm.

That depends on how fast you are driving, but given it's getting colder it's a bit of a non-issue at the moment! Also, it it's a VAG car then it is possible to switch the AC compressor off with the ECON button to save fuel.

mutley74

I was just curious I do lots of A roads and Motorway miles but guess hit a few lights and a railway crossing so could be overall idle time about 10mins a day.

Ultrasonic

I should perhaps have said my figure above is with all ancilliaries swtiched off.

If you've got a properly designed stop-start system you may as well use it. You'd at least hope that a starter motor designed to cope with this has been fitted. It won't make much difference for mostly motorway driving though.

mutley74

Ultrasonic wrote: »

I should perhaps have said my figure above is with all ancilliaries swtiched off.

If you've got a properly designed stop-start system you may as well use it. You'd at least hope that a starter motor designed to cope with this has been fitted. It won't make much difference for mostly motorway driving though.

agree wont make any use when car is in motion, but kicks in at every light and junction as soon as its in neutral, kicks back on instantly when gear is selected.

bigjl

According to the fuel computers I have had in cars over the years and my odb reader with a App would suggest around 0.1l per hour.

I used a Merc S350L cdi for a few days earlier this year doing a bit of chauffeur work and I turned the stop start off as it sounded like the engine was falling out when it restarted.

I have used a Prius and that was super smooth the Merc system in the S class diesel has been noted to be a bit rough in some reviews.

I turned it off when I had a punter in to be honest.

Never noticed any improvement in economy but I would suspect there would be one.

It did over 50mpg at a steady 70mph which was a pleasant surprise.

That vehicle was a 12 plate with 30k on it at the time.

A better engineered and smoother system would definitely be a good thing for any primarily urban driver.

harleq1962

starting the engine is where most of the wear and tear is done to the engine,
http://www.caranddriver.com/features/gas-pains-mileage-myths-and-misconceptions-turning-off-the-cars-engine-saves-fuel-when-the-stops-are-long-but-its-not-a-good-idea-for-short-stops-page-7

mutley74

harleq1962 wrote: »

starting the engine is where most of the wear and tear is done to the engine,
http://www.caranddriver.com/features/gas-pains-mileage-myths-and-misconceptions-turning-off-the-cars-engine-saves-fuel-when-the-stops-are-long-but-its-not-a-good-idea-for-short-stops-page-7

I had a Hyundai i30 on hire for 2 weeks recently with start/stop..when the air con was on the start/stop did not always kick in due to engine load. When I was not using air con, s/s kicked in more often when engine was not in use. So I guess the technology is more advanced now to avoid situations of misted windscreens when waiting.
If I am waiting in a heave traffic queues (unless its very dark) I usually turn my headlights from full beam to dipped level to reduce engine demand.