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Terrible terrible mpg issue

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Rays18, Feb 21, 2013.

  1. Rays18
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    Rays18 East Tattoo

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    [Feb 21, 2013]
    So basically Im getting 100miles to £20 diesel (1.9tdi) @£1.40ish per litre
    Car was serviced just before Xmas.

    Anybody any other ideas what the problem could be?

    Thanks !
    #1
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  3. mattyb6
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    mattyb6 Active Member

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    [Feb 21, 2013]
    Same problem mate, I get 30mpg like you in the same ccar also mine was service recently.
    i think it could be my thermostat, and temp sender, making the car run colder, and this making the ecu over fuel it.

    I've cleaned my egr too, but I think a turbo clean, and some injector clean will help mine run a bit more efficient.
    #2
  4. adamss24
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    adamss24 Well-Known Member

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    [Feb 21, 2013]
    Do it brim to brim not by putting 10-20 quid worth of fuel ! Reset the odo after filling and drive it as you normally do !
    #3
  5. Mike.M
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    Mike.M Well-Known Member

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    [Feb 21, 2013]
    Then after a week fill to the brim again. And note the miles and amount of fuel used to brim it again.

    Try to also use the same fuel pump to be accurate
    #4
  6. Rays18
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    Rays18 East Tattoo

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    [Feb 21, 2013]
    You mean the likes of Wynns or Millars will do the trick?
    Im going to change oil and filter this weekend when I get a chance, hopefully that will work.
    When I got the car last June, I was literally getting around 80miles to £10 diesel !

    So much for eco diesel ey hahaa.
    Better off buying 1.8T !!
    #5
  7. gavsman
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    gavsman Member

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    [Feb 21, 2013]
    2 things won't have helped with your mileage.

    1) diesel was about 135.9 back in June
    2) the cold weather - taking your car alot longer to warm up, which would mean using more fuel.

    Also does your coolant dial on the dash go up to 90 ( bang in the middle)
    #6
  8. Mr-C
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    Mr-C Active Member

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    [Feb 21, 2013]
    £20 does not get you so much fuel these day
    #7
  9. crazy88
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    crazy88 Loving the anonymity

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    [Feb 21, 2013]
    What roads are you normally driving? Mine is a mum mobile these days and rarely sees anything more than 30mph on short journey. I aim for about 400 miles on a full tank. However, when on a run it performs very nicely and if I only did motorway miles I reckon I could get 600 out of a tank. Diesels are poo at pottering around.

    Also, has anything else changed? I fit new wheels which are wider and my mpg dropped too.
    #8
  10. stu_m
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    stu_m Well-Known Member VCDS Map User

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    [Feb 21, 2013]
    I usually use a certain petrol station (total) and always get decent mpg the other week I filled up at morrisons and ive got less then 40mpg out of the full tank

    if you have used a different fuel this could be it supermarket fuels are **** this is tried and tested by me in the past and god knows what I was thinking when I filled there the other week!!

    If nothing has changed with the fuel then it could be a number of things

    first thing to do is brim it and work out mpg on tank to tank fill ups as mentioned then get back to us
    #9
  11. Springer*
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    Springer* Member

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    [Feb 21, 2013]
    Based on current prices, 100 miles from £20 of diesel isn't terrible terrible economy in this weather...

    £20 of diesel based on 142.9p per litre = 13.99 litres.
    13.99 litres = 3.07 gallons

    100 divided by 3.07 gallons = 32.57mpg

    This will no doubt consist of a fair bit of cold starting and town driving too... okay, its not great but its hardly terrible.

    How do you drive? Heavy right foot? Gearchanges?

    Need more info to get an accurate idea of any problem buddy..

    Get a vagcom scan done for error codes to start with and see what comes up.

    Could be anything from clogged fuel filter, EGR, MAF issues, poor fuel, thermostat issues etc..

    J
    #10
  12. Rays18
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    Rays18 East Tattoo

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    [Feb 22, 2013]
    Cheers for the replies folks.
    Em first off Id usually use the same fuel pump. Maxol (N.Ireland)

    I wouldnt say Ive a heavy foot at all, its only 100bhp at the end of the day lol. Not much you can do anyway.
    Usually more short journeys as I only work 10 miles away from home.

    Looks like Ill have to get it hooked up with Vagcom and see what it says.
    #11
  13. StuG808
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    StuG808 1.9tdi130 Avant FailWheelDrive

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    [Feb 22, 2013]
    So how do do you know that you got 100 miles to twenty quid? Was it empty and then after 100 miles you ran out of fuel? ;)

    I guess you were doing it based on the fuel light, but how accurate is that? Think of all the fuel splashing about in the tank and the dampened fuel needle.. Plus a hundred miles is too low a distance to get a balanced reading. Brim to brim measurements are the only way to get a mpg reading.
    #12
  14. 666markyboy
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    666markyboy Well-Known Member

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    [Feb 22, 2013]
    It really does depend on how, and the types of road you drive.... my 1.9 TDi Quattro Avant is a heavy car but on the motorway cruising at 60 and being very carefull i can get it up to around 48 MPG but scooting round the streets not being particularly cautious and enjoying myself i can get it down to low 30's quite easily
    #13
  15. AndyMac
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    AndyMac Moderator Staff Member Moderator

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    [Feb 22, 2013]
    33mpg is about average for short journeys/town driving - there's nothing wrong with the car - that's what you'll get this time of year.
    No need to brim the tank and all that nonsense, the extra weight of a full tank will reduce your mpg even more!
    I get the same in my 130 TDi, but cruise on the motorway and it shoots up to 48-55mpg
    #14
  16. Mollygoogle
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    Mollygoogle Member

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    [Feb 22, 2013]
    The weight of a full tank will have virtually zero effect on your economy and will be more than offset by the additional trips to the fuel station.

    A full tank of fuel weighs about 50kg so equivalent to about 3% of the vehicles total weight. If you compare that as a difference to half a tank then it only becomes 1.5% of the vehicles total weight. So even if you assumed a direct correlation between weight and economy it would only be a difference of about 0.75mpg based on 50mpg. In reality weight is only an issue when accelerating from 0mph, if the vehicle is already moving, say at motorway speeds the difference in efficiency by increasing or reducing a vehicles weight by that of half a tank of diesel would be minute at best. Offset that against distance travelled to the fuel station, lost vapour through repeated opens of the tank, etc, then you save absolutely nothing by not brimming the tank.
    #15
  17. stu_m
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    stu_m Well-Known Member VCDS Map User

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    [Feb 22, 2013]
    the OP says he works 10 miles from home which is the same as what the missus does in my car everyday

    she averages 44 minimum in this weather on that run this is a mixture of stop start with a couple of very short 40 limits and a 4 mile stretch of constant 30 then last mile of stop start
    #16
  18. Mollygoogle
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    Mollygoogle Member

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    [Feb 22, 2013]
    I would cry if my 130 got down to a 33mpg average
    #17
  19. Rays18
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    Rays18 East Tattoo

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    [Feb 22, 2013]
    Yeh am just going by the fuel light and reset trip counter every time I fill up.
    Will be servicing tomorrow hopefully weather permitting so will update by Sunday maybe.
    Hopefully it all works out
    #18
  20. glenandem
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    glenandem Member

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    [Feb 22, 2013]
    Hi guys I replaced my cambelt a few weeks ago right as the temps dropped and I'm not sure if its the weather or something to do with the cambelt change even though it runs sweet, I even blocked the egr that same weekend and my mpg seemed to have gone down since then, just around town driving I was getting 40-42mpg and now I'm getting 35-37mpg according to the dis and that's at average speed of 14mph too, If I put £20 I get about 120-140 miles out the car, I think I'd get more if I did long runs but we only do a few miles a day, I'm just waiting for the temps to rise as I've replaced the temp sensor,thermostat, blocked egr and full service with no vagcom faults??
    #19
  21. adamss24
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    adamss24 Well-Known Member

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    [Feb 23, 2013]
    I would not keep a diesel tank low on fuel, there are nasty bacteria that thrive in the wet, dark and hot fuel/water mixture. Once that bacteria has past your fuel filter is game over for the engine ! The byproducts of the bacteria are so acid that it disolves the fuel lines and seizes the injectors/pumps when it occurs.
    As mentioned above, fill to brim, reset you odometer, drive as usual for 62 miles then brim the tank again- that will give you an accurate reading ! Going by the fuel light is never accurate enough, with fuel sloshing around is easy to have froth at the bottom of the tank which fools the gauge into thinking there's more fuel than it's actualy is ! 33Mpg is not too bad with late weather especialy if OP is doing short trips which does not get the engine up to normal operating temperature ! Hope this helps !
    #20
  22. PAULF
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    PAULF Active Member

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    [Feb 23, 2013]
    Thread Drift Warning!!

    I believe you are on about cladosporium resinae (sp?) which is a bugger if you get it.
    It does live in diesel, but prefers Kerosene if given a choice.

    It isn't very common in the UK, due to the cold weather. If you keep the tank low on fuel, you get condensation. 'Gladys' lives on the fuel/water boundary so condensation will encourage growth. You will first notice a brown slime in the fuel filter if you have it. The excretion products won't cause any problem in a plastic tank - but as Chris says, it is acidic. Your lines and injectors should be safe if you run the car every few days. There are products to kill it off, and to prevent reoccurrence. I have a stock of Biobar (for my heating kero) that I 'found'. The problem with the shock treatment is when it dies, it then goes through your system and clogs everything. It is easy to wash the slime out though.

    ​Back on topic


    As everybody says, brim it, zero odometer, drive it, note milage, brim it, work it out.
    This is the only way to check your MPG properly. We use the app 'road trip' for our cars religiously and it is a good indication of the health of the car.
    #21
  23. DeNi
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    DeNi New Member

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    [Mar 13, 2013]
    I have got same problem, badly low mpg... 20mpg(round town drive brim to brim) on 1.9tdi (130)multitronic . Now outside is +3c, starting a car, let it work for 1-2min, then i need 15min!!! of round town drive(not in slow motion) to get it up till 90c is that normal? (has new thermostat) once it reached 90c,stays there forever. So i have 20mpg in town and 45mpg on long motorway trips.

    My question is : Is that normal that this car needs that long to warm up till 90c? or something wrong with it? (scanned for faults,no faults at all,new thermostat) please help.
    #22
  24. billybaggins
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    billybaggins New Member

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    [Mar 25, 2013]
    Rays18 , or anyone find out if this was weather related or not? my tdi 110 is getting similar and i thought id be getting more.
    #23

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