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gambit

poor fuel economy

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Hi all,

I have a 520 d F10 2011 plate no mods.

Fuel economy is really poor and I only seem to get 25 mpg for local travel around between home and town and work (4 miles away). If I use some slightly extra urban roads for a longer distance say 20 miles  it can increase to 30 mpg but this is still so bad in my opinion. Can someone please help with this? Is there a cheap remedy to this if a common problem? Any questions please ask. I've owned the car about 4 years. Fully serviced etc.  It never used to be like this.

Many thanks!

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I don't know how the 520d cooling system compares to the 6-cylinder models, but thermostat failure is common on 6-pot diesels and can cause high fuel consumption. Lots of info on here, and how to check coolant temperature if you don't have a temperature gauge. Have a dig around.  :)

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You definitely have a problem as your mpg is worse than mine!

 

A journey of 4 miles will be slowly killing your Diesel. It will be nicely furred up on the inside. EGR will probably be clogged up.

 

It will most likely need de-coked on the inside. And your DPF will be in dire need of a regen.

 

Give it a full service a tank full of super diesel and go and take it for a long run (30miles+) at motorway speeds. Check your hidden engine temps on this run too to rule out thermostat problems as mentioned above.

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Good advice but also keep gearbox in manual and hold the revs high (not sure what high is on a derv - 3000?) because otherwise the box tends to keep the rpm too low.

 

I occasionally do the same in my n53 petrol engine car as it has a separate catalyst for nox which needs sustained high engine speed to burn off. 

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As a matter of routine especially if recent journeys have been in heavy stop start and slow traffic, or periodically observe the fuel consumption when it starts significantly dropping I select manual using a lower gear to keep revs high generally around 2500-3000 rpm, I set the cruise control to hold it at those revs for 10 -15 minutes, after driving for 10 -15 minutes then reset the fuel consumption, select drive and drive normally you should then see a marked difference in fuel consumption, I also do the same to our Mini Cooper 1.6d, and in doing this periodically I have never seen the DPF light come on so it must be keeping the Diesel Particulate Filter free from excessive soot build up, which indirectly relates to better achievable fuel consumption.

Currently my F11 520d has achieved 51.7mpg which was a mixture of 90% motorway driving average speed of 70mph ish, and 10% heavy stop start traffic average speed 0 - 40mph.

The lowest fuel consumption I have observed is 44mpg driving in London and after that it needed a good blast out to get fuel consumption back to a more normal figure for mixed driving 47.2mpg.

Because your mpg is so low you may have other issues as well, also as I believe your F10 520d year suffered timing chain issues so I would be carefull not to overev it, others on this forum will have better knowledge & advice regarding that issue than me, from what I have been told my own 2014 F11 520d timing chain issue has been resolved!

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Lots of great rplies thanks!

 

i should have mentioned its an auto! 62k miles.  Had full service last july.

 

so what is my plan of action here ?  On other advice I was going to buy Forte - 3 bottles of. One dpg cleaner, one diesel cleaner one turbo cleaner. Is this worth doing?

 

also i think i might know how to access the secret menu for temp - which temp am i looking for and when do I read it- during or after the journey.  I take it this step will determine if stat issue? So should I just do thia first before adding the stuff? Thanks again!

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Consider running a can of BG244k (available for around £20) to see if helps clear the engine up. That is awfully low MPG. Give it a can, a few small runs and some decent ones and see how the engine is performing. 

 

Tyre pressures, fuel quality and many other factors come in to play but short journeys will be the killer

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I'm not a diesel man but Forte injector cleaner has always served me well. First time I used it on my E39 540 I got nearly 20% improvement in fuel consumption. Ok I was only getting 19mpg before but improvement was noticable.

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gambit - I had already assumed it was a auto just move the auto shift to the left and select the appropriate gear, my advice is more important especially with a auto box because the engine is kept at low RPM most of the time, I try would the no cost option first, drive the car in manual shift to keep revs constant about 2500 RPM for about 10 - 15 minutes, reset the fuel consumption via the i drive then select shift back to drive, drive normally for a few miles if you don’t see a improvement in the fuel consumption, you can still use a fuel additive to clean the DPF.

Did not mention before but my 520d does not like Tesco diesel there is always a drop in fuel consumption by 2--3 mpg, but all the other regular grades are fine including Asda Sainsbury's, and about every 3rd or 4th tank of diesel I use the Shell V power whether it does any good at cleaning the internals or not I cant say! I certainly dont notice any difference in performance or fuel consumption using it.

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20 hours ago, gambit said:

Hi all,

I have a 520 d F10 2011 plate no mods.

Fuel economy is really poor and I only seem to get 25 mpg for local travel around between home and town and work (4 miles away). If I use some slightly extra urban roads for a longer distance say 20 miles  it can increase to 30 mpg but this is still so bad in my opinion. Can someone please help with this? Is there a cheap remedy to this if a common problem? Any questions please ask. I've owned the car about 4 years. Fully serviced etc.  It never used to be like this.

Many thanks!

 

If you make so many short trips, you really need a petrol engined car. Your DPF, catalytic converter and EGR valve are probably all gunged up.

 

You need to firstly double the number of oil changes, use a low SAPS oil, change all the filters, only use premium diesel fuel, and give the car a good one hour run every two weeks to get everything up to operating temperature.

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I do a 60 mile round trip commute A roads and motorway and my 520d returns 47 mpg but driven with a bit of thought I've seen 51 mpg. My wife used it for work a few weeks ago for a week and her drive is through rush hour traffic and only 7 miles so plenty of stop start driving and the difference in the car afterwards was notable it did feel quite sluggish. Again a good run and it was back to normal.  

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On ‎6‎/‎22‎/‎2018 at 12:45 AM, gambit said:

Hi all,

I have a 520 d F10 2011 plate no mods.

Fuel economy is really poor and I only seem to get 25 mpg for local travel around between home and town and work (4 miles away). 

 

I'm not sure but I think diesel engines take a lot longer to warm up than petrols, so perhaps that is why the mpg is so disastrous compared to what it would be with long hot running.  

Edited by Tuvoc

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Hi guys,

 

Sorry was away for the weekend.  Many thanks for the replies once again.

 

So I did a long distance journey with motorway miles at least 50 each way hitting over 70 mph at times but forgot to reset the onboard journey thing, and the mpg came out 38 from being 30 before.  Also I wasn't really able to remember to do the temp check thing.  This is still bad mpg right?  Anyway had a look and Halfords do a DPG clean for £85 so rather than get the Forte stuff has anyone had this done and did it work?  I do do long distance now and then throughout the year so when the mpg was good this car was very economical for that purpose so just want to get it back that way.

 

Kind regards

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14 minutes ago, gambit said:

Hi guys,

 

Sorry was away for the weekend.  Many thanks for the replies once again.

 

So I did a long distance journey with motorway miles at least 50 each way hitting over 70 mph at times but forgot to reset the onboard journey thing, and the mpg came out 38 from being 30 before.  Also I wasn't really able to remember to do the temp check thing.  This is still bad mpg right?  Anyway had a look and Halfords do a DPG clean for £85 so rather than get the Forte stuff has anyone had this done and did it work?  I do do long distance now and then throughout the year so when the mpg was good this car was very economical for that purpose so just want to get it back that way.

 

Kind regards

yes, 38 mpg on a run is terrible for a 520d, my 3.0d can quite comfortably get 50mpg on a run. Id get a specialist to take a look if you aren't handy with codes/spanners

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23 minutes ago, paperjams said:

yes, 38 mpg on a run is terrible for a 520d, my 3.0d can quite comfortably get 50mpg on a run. Id get a specialist to take a look if you aren't handy with codes/spanners

 

my fault I know but if I'd reset the computer I'm thinking the lower figure already in from previous journeys (and quite a bit clocked up) has brought the average down has it not?  I'll be sure to reset it next time hopefully v soon.  I still think the dpg would be worth a clean so am happy to take it Halfords if people know about it?

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I have my trip computer to reset each day, on a motorway journey like the one you describe I'd be getting mid 40's from a 535d. I'd expect much higher from a 520d.

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12 minutes ago, sjj84 said:

I have my trip computer to reset each day, on a motorway journey like the one you describe I'd be getting mid 40's from a 535d. I'd expect much higher from a 520d.

Yes  as stated however as it was not reset the figures are probably skewed by a low mpg from several previous journeys.

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2 hours ago, paperjams said:

Ah yes, I see your point. Maybe worth another attempt! I had this done on my car a few months back and made a big difference.. http://www.enginecarbonclean.com/

 

I am making enquiries with enginecarbonclean.com as they look good and given what Andrew said about Halfords.  It seems they charge £99 quid but this does not appear to include the DPF cleaning.  Next chance I get I will look and report on temps.  thanks

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Gambit:

Car on motorway in manual in 4th at 60-70 a number of times.

Powerenhancer.co.uk or ebay for Forte products or Archoil products. Both superior in the industry...and of course the trusty BG244 etc.

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7 hours ago, gambit said:

 

So I did a long distance journey with motorway miles at least 50 each way hitting over 70 mph at times but forgot to reset the onboard journey thing, and the mpg came out 38 from being 30 before. 

 

So 30 went up to 38, which meant the motorway mileage itself might have been 45+

 

As you say, re-set it next time :-)

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Hi as an update:

 

First: Not been able to do a long run yet but have done some short drives on urban roads and checked temperature and was giving 88 on one occasion and 106 another.  Now, given the recent hot weather as these temps possibly skewed? I suspect they may be but I also think that the temp is climbing correctly so not a stat issue can anyone please confirm.

 

Second: I have the Fort bottles and rang them to ask advice.  They said it is only to be used by the professional trade (says on back too) and can't be sold to retail so can't give it advice and that they don't sell it online  What does this mean that I cannot use it?  Has anyone used them on their F10? Also they were like you cannot buy it elsewhere but is being sold all over the internet and people buying and reviewing it with positive results.

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I used Forte for years on my E39 540 and for the last year on my E60 550, always with positive results. I find that a bottle every six months is as effective but cheaper than running a tank of super unleaded from time to time ( I'm doing fairly low mileage at the moment). It was originally recommended to me by a mechanic who swore by it. He used two bottles to a tank of fuel on poorly running cars, I've only ever used one bottle per tank as that has always been sufficient. Before that I used Reddex which does the same job but nowhere near as well. There are many other additives about that probably do the same job but I haven't used them to be able to comment.

 

Forte saying it is for trade use only just means they only want to supply in bulk and prefer to deal with trade rather than individual customers. This is not uncommon and as you pointed out it is readily available on the internet.

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