ok I have a diesel bmw x5 and over the past few months mpg has gone down had a full service but made no change had it at a bmw specialist to day on diagnostics and 3 of glow glugs and down the car starts fine tho so what am asking can glow glug effect mpg and performance ? the guy there said this could effect mpg any one else have a view on here

Its my understanding that the glow plugs only ignite the fuel on start up, conmbustion is maintained by compressing the fuel air mixture during the piston stroke. Did you change the auto box fluid and filter at service, check yr Ac pump isn't jammed on etc, im no expert but i don't think its the plugs however with winter approaching id change them anyway.

I was reading the plug can ignite when you put your foot down on a few bmw fourms some people claim a rise in mpg after fitting new plugs so am unsure

Its my understanding that the glow plugs only ignite the fuel on start up, conmbustion is maintained by compressing the fuel air mixture during the piston stroke. Did you change the auto box fluid and filter at service, check yr Ac pump isn't jammed on etc, im no expert but i don't think its the plugs however with winter approaching id change them anyway.

 

Mine too..... Although with modern diesel engines and the wonderful magic ways they keep down emissions and fuel consumption, anything is possible....!!

The glowplugs will make little or no difference to mpg after the engine has started. Out of interest what has the mpg dropped from/to ?

Does it smoke normally ?

Does it smoke when you accelerate?

Has the air filter been replaced ?

Does it 'feel' like it's running normally ?

Have you run any injector cleaner through it ?

MPG goes down with cold weather anyways .. by around 3>5mpg

Don't know much about diesels at all but the mpg in my vectra dropped from 54 to 13 for a while. Made me wonder what the hell had happened but it turned out that it does this while clearing the diesel particulate filter. Did a few miles in top gear and it cleaned the filter and the mpg returned to normal. Maybe your one has failed? Just a thought

The glow plugs just warm up the ignition chamber, the high pressure causes enough heat to ignite the fuel once the engine has fired up. So it won't be glow plugs. Also as mark says engines are at their best in warmer climates. So in winter you will see a drop in MPG. May sound silly but have you done all your routine maintenance, tyres checked for correct wear and all inflated properly. Was the service a full service? ALL filters etc?

 

Goof luck and keep us informed

search for something called terraclean, tried it and it works. especially one diesels.

My mpg went up by 9 mpg on average

Just one point from earlier, engines are only at their best in warmer climates if you assume lots of short journeys, as it takes far more fuel getting the engine up to running temps. An engine will generally run much better when it's cold, with nice damp, dense cold air. So long journeys in cold weather should give the same or better mpg than an equivalent journey in hot weather.

The glowplugs will make little or no difference to mpg after the engine has started. Out of interest what has the mpg dropped from/to ?

Does it smoke normally ?

Does it smoke when you accelerate?

Has the air filter been replaced ?

Does it 'feel' like it's running normally ?

Have you run any injector cleaner through it ?

 

smokes when you put you foot down feels ok maybe a little weaker I have just started using millers ecomax treatment to see if that help clean it out my mate as the same car and hits the 30mpg on a run I did a run few days a go 200miles and only got 26.5 mpg

EGR Valve. Most can be removed, cleaned and re-fitted. Not sure on the BMW tho ?

 

Made a whore of a difference on my TDCI Mondeo.

And my mates 2.7 Cherokee Jeep.

 

Alan..........

EGR Valve. Most can be removed, cleaned and re-fitted. Not sure on the BMW tho ?

 

Made a whore of a difference on my TDCI Mondeo.

And my mates 2.7 Cherokee Jeep.

 

Alan..........

 

I'm with Alan on this, it can be a problem with the beemer 3.0d engines. Not sure on the newer cars but the older 3ltr unit is pretty easy to do away with the EGR. If it is the cause or your problems you will need to strip out the valve clean and refitt it then just blank off the vacuum pipe job done.

 

Regards the glow plugs, they are usually timed to operate for a short period before you turn the engine over to start it ( ie the light on the dash ) so can't see who they would affect mpg. Been a while since I was on the tools though and there could be some new technology that uses them for purposes other than starting, cant see it though as once the engines warm whats the point.

I find that a good service tends to increase the mpg a little, but it is mainly my driving style that affects the mpg. Tonight it was low at around 36mpg, doing the speed limit honest officer, but if I trundle at 60 I get high 40's from a CLS320. Its also a 3.0L TT, just a diesel version!