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1.9tdi mpg gone down now it's colder

Discussion in 'A4/A4 cabriolet/S4 forum(B6 chassis)' started by Ian2012, Oct 13, 2013.

  1. Ian2012
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    Ian2012 Member

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    Has anyone else noticed this? i have been getting easily mid 50's now am down at 49-51mpg, oddly enough the hotter the outside air temp over the summer the better mpg i was getting. is this normal with diesel's?

    Ta
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  2. @udi A3
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    @udi A3 Active Member Site Sponsor

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    Rain = drag and extra wieght on the tyres... could explain why im seeing 46 not 56 now...
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  3. B5NUT
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    B5NUT Well-Known Member

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    Yes very normal, colder air is denser so the engine uses more fuel to compensate but you should get a little more power, but won't be that noticeable
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  4. JimmyH
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    JimmyH Member

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    It's actually due to the anti freeze additive the refinery add the stop diesel slidifiying, this reduces the cetane rating thus MPG slightly drops.
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  5. adamss24
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    adamss24 Well-Known Member

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    Not entirely true, cold weather the engine uses more fuel to get to operating temperature hence the Mpg drop. Winterized diesel is not introduced till late november if the weather forecast is well below zero celsius.
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  6. Ian2012
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    Ian2012 Member

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    Time to compensate with some additive then.
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  7. demus
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    demus Member

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    Quite natural, stop worrying, the colder the engine the more fuel it will use till up to temp, plus extra electrical loads etc.....
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  8. glenandem
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    glenandem Member

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    yep mine went down from averaging 39-40 in the summer to 34-35 last winter with the snow but just this last week ive noticed its gone down to 38 so its dropping with the temp!
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  9. Ian2012
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    Ian2012 Member

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    Wow never thought it would make that much difference, it's like 10% or so
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  10. S4_dan
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    S4_dan Fire up the Quattro!

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    So would adding a cetane booster to the fuel make much difference?
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  11. DieselJake
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    DieselJake God Mode

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    From my experience it just provides a placebo effect.
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  12. @udi A3
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    @udi A3 Active Member Site Sponsor

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    I put a can of injector cleaner from kwik fit through it yesterday and im back up to 56mpg :D
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