rootsy
Member Since: 04 Aug 2009
Location: Newbury
Posts: 11
  
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What is the most likely cause of an overnight (literally) drop in mpg
Ever since owning the car I have usually got 30/31mpg but suddenly about 3/4 weeks ago I started (and still am) getting about 23mpg, even when driving like a vicar?
Any thoughts? (I did change to ATR's around that time...)
Cheers
Marc
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 13th Jan 2010 5:22 pm |
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DiscoDunc
Member Since: 08 May 2006
Location: Bristol
Posts: 16390
 
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check your brake calipers are not sticking - the disc/wheel will be a lot hotter on the wheel that is sticking.
Or the EPB could be binding.
could be loads of other things as well but those are the two i would check first.
I woudlnt have thought the tyres would make that big a difference. I changed from road tyres to Cooper ST's and didnt notice any change in MPG.
if you are passing M4/M5 junction pop in and i will test the discs with my IR thermometer Duncan
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Last edited by DiscoDunc on 13th Jan 2010 5:28 pm. Edited 2 times in total
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| 13th Jan 2010 5:26 pm |
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wiggs
Member Since: 03 Sep 2006
Location: Manchester
Posts: 14368
 
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I have used AT2's on my previous D3 and lost about 3 mpg with them on .
On the G4 its about the same loss with MTR's G4 Gone ...but not forgotten
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| 13th Jan 2010 5:27 pm |
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WOODY179
Member Since: 01 Jun 2005
Location: Chesterfield
Posts: 3637
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FBH has probably been uing a lot more fuel over the last 4 weeks too -especially if you'e been doing a lot of short journeys. 1996 Discovery 1 300TDI ES Biarritz Blue, sold
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| 13th Jan 2010 5:36 pm |
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NeilD
Member Since: 01 Dec 2008
Location: Sunny Surrey
Posts: 4845
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All of the above. Also it might be worth checking the intercooler is clear (the double radiator grill type thing on the front). If you went through the muck at Salisbury it might be a little claggy.
Note: do not jet wash, take a look on the site at the best way to clean/check - wait till the cold waether has gone though - you dont want it frozen.
Equally check the air filter too.
23Mpg is quite normal though for many, not heard of a real 31Mpg on normal use myself.
Us South East lot might be meeting up to have group intercooler clean up next month, you'd be welcome to join us. My Youtube Channel http://www.youtube.com/user/NeilDisco#p/u/5/Dz4-Q95GQ2c
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| 13th Jan 2010 5:50 pm |
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rootsy
Member Since: 04 Aug 2009
Location: Newbury
Posts: 11
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Thanks for the suggestions,
I will have a look at the brakes and intercooler tomorrow (hopefully the snow is starting to clear which will make it easier!)
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| 13th Jan 2010 6:04 pm |
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Jack
Member Since: 18 Feb 2006
Location: Greater Manchester
Posts: 47
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Had a similar drop myself, 23ish to 19 plus lots of black smoke. Just changed the air filter tonight having read a recent post suggesting that could be the cause, so heres hoping.
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| 13th Jan 2010 7:10 pm |
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Mollers
Member Since: 01 Jul 2009
Location: Mighty Penryn - Cornwall
Posts: 116
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I had a new set of GY Wranglers fitted and a full laser alignment and lost a couple of MPG. Not sure that 31 was realistic. How often did you zero the comp.?
A couple of pounds extra tyre pressure can make quite a difference. Our auto HSE gives 23/24 around our hilly local area and 27/28 on a run depending on load.
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| 13th Jan 2010 7:38 pm |
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rootsy
Member Since: 04 Aug 2009
Location: Newbury
Posts: 11
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I zero the computer on every fill up and would always watch the mpg display like a hawk, must be an ocd thing! (don't know why though as I never look at how much the diesel costs at the garage)
I have also zero'd it whilst going at a steady 60mph which usually results in some excellent mpg figures! but not any more, it still goes down to 23-24mpg quite quickly??
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| 13th Jan 2010 8:02 pm |
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Willy Eckerslike
Member Since: 12 Jan 2009
Location: N Yorks
Posts: 1612
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I had this on a D3 turned out to be an EGR valve, it didn't knock perfromance too badly just moved the power further up the rev range, If i remember right you don't necessarily get an engine light. But bear in mind the early D3's weren't as good on juice as the later ones. Club Pie n Pea
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| 13th Jan 2010 8:11 pm |
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Iain G
Member Since: 31 Jan 2009
Location: Filey
Posts: 430
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I changed from road tyres to MTR's which made a drastic drop in MPG but not as bad as yours. I was managing 36 mpg with the road tyres but this went to 31 with the MTR's. Needless to say I am on the lookout for another set of tyres / rims to put back on when (or if) the weather brightens up.
I was sick of the FBH cutting in all the time recently as sometimes I make numerous journies in a day, so once the FBH has done its first warm up in the morning I remove the plug for the rest of the day.
Iain
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| 13th Jan 2010 8:12 pm |
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Duncster
Member Since: 25 Nov 2006
Location: Midlands
Posts: 755
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Mine has droped to 16 mpg for the last 2 weeks on a tankfull never ever got more than 23mpg. We do lots of short journeys and long ones usually are towing. I could only dream of 30+ mpg
Just about to put some new tyres on can't see that would make huge improvement though 15 3.0 RRS HSE - Silver
05 2.7TDV6 S AUTO Silver - Retro-fitted Leather.
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| 13th Jan 2010 8:39 pm |
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The Large One
Member Since: 20 Apr 2007
Location: Down the polytunnel
Posts: 6143
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What mileage ??
service schedule for air filter is 45k
from previous findings by members it seems to be a service too far and by the time 45k comes round it's choked, seriously affecting MPG
have a look at it...for the cost it will be the cheapest first place to start TLO has left the building.......
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if you would like to order anything just give me a shout
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| 13th Jan 2010 11:06 pm |
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Duncster
Member Since: 25 Nov 2006
Location: Midlands
Posts: 755
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TLO - I change Air Filter at every service as you say cheap to replace 15 3.0 RRS HSE - Silver
05 2.7TDV6 S AUTO Silver - Retro-fitted Leather.
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| 13th Jan 2010 11:55 pm |
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frogall
Member Since: 29 Aug 2008
Location: Norfolk
Posts: 250
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Don't think the EGR valves open so quick in cold weather - with that and switch to AT2s and lots of FBH going on my mpg has dropped from 32 average (reported on dash so about 30.5) to 28.5 in the cold.
Having said that - first over 100 mile journey for a few weeks brought it back to 31 so not bad. I'm on a whisky diet. I've lost three days already.
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| 14th Jan 2010 12:05 am |
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