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Optimum rev range for fuel efficiency

Discussion in 'Audi S4/A4/A4 Cab (B8 Chassis)' started by allanmb, Mar 21, 2014.

  1. allanmb
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    allanmb Member

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    [Mar 21, 2014]
    Does anybody know what the optimal rev range is for getting the best fuel efficiency? For example:

    In a 20 zone on the flat, I can choose 3rd gear at just over 1200rpm or 4th at just under 1000.

    In a 40 zone I can choose 5th at just over 1300rpm or 6th at just under 1100.

    My feeling from looking at the dis, is that in the 40 zone it is best to be in 6th but I'm unsure about the 20 zone. I have to stress that the road is dead flat and I'm not putting any excess load on the engine. It doesn't labour at just under 1000rpm in these conditions but I want to know if it would be better off going for the lower gear and slightly higher revs?
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  3. Liquidfusion
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    Liquidfusion Active Member

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    [Mar 21, 2014]
    I find it best to change gears just before it goes over the 2000 rpm rev
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  4. allanmb
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    allanmb Member

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    [Mar 21, 2014]
    That's what I do too when accelerating but when going at a constant speed for a long time I try to minimise the revs add much as possible
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  5. benjie
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    benjie Active Member

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    [Mar 21, 2014]
    Our 140TDI Passat would have us in 4th at 20 I think. I don't like it as the engine labours like hell if you need to speed up in the slightest, but like you say, it's a flat road. I'd say 4th. You can check which is most efficient by putting the DIS in current fuel consumption and drive the road in both gears, seeing what the car reads.

    Incidentally, after 2 weeks, the best rev range for fuel economy in my S4 (regardless of speed) is somewhere between 0 and 0!
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  6. desertstorm
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    desertstorm Well-Known Member

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    [Mar 21, 2014]
    I have found that optimum rev range for fuel economy when bimbling around is 1200-1400 rpm.The three litre I have is happy enough at 1000 RPM in 4th or 5th but I don't think thats the most fuel efficient.
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  7. DieselJake
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    DieselJake God Mode

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    [Mar 21, 2014]
    Lowest rpm possible in the highest gear you can with granny acceleration towards saud gear. No fun though.
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  8. allanmb
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    allanmb Member

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    [Mar 21, 2014]
    I know that feeling. I have come from a 3.2 Quattro which wasn't particularly fuel efficient, especially around town!
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  9. allanmb
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    allanmb Member

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    [Mar 21, 2014]
    This is my feeling too, but it would be nice to know definitively...
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  10. Anthony566
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    Anthony566 Active Member

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    [Mar 22, 2014]
    I use the in car gear change indicator as this seems to request a change before 2000 for every gear :)
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  11. rum4mo
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    rum4mo Active Member

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    [Mar 22, 2014]
    I tend to find that the difference between "granpa'ng" it and driving it normally is not too much, maybe just a bit better driving it normally, driving it like a sporting type of car will end up with much more fun accompanied by worse economy, but that makes sense and sometimes the rewards of playing out do the higher costs - though that is part of what an S4 is about - I believe Skoda make a Superb car for folk that don't like spending money!

    Though I do like to boast about the crazy - maybe 30MPG that I get commuting when others in "lesser/smaller" cars only get 33MPG, or these strange/different people who drive 3 miles max per day to work, have a DERV engine, get about 30MPG and don't use their car for long journeys ever - how weird/different is that .

    Petrol, yum yum!

    I accept that I am departing from the original poster's intentions here, I'm just responding to a later posting - and probably making the case to choose an S4 over a 3.2 Q any day, I was originally aiming to buy a second hand 3.2 A4 Q - but availability and the hard facts behind the differences if ending up with the wrong spec made me make the leap from 2.8V6 B5 Passat 4Motion to B8 S4 .
    Last edited: Mar 22, 2014
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  12. benjie
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    benjie Active Member

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    [Mar 22, 2014]

    Agreed, totally. Apologies for pulling the thread off course! (220miles from my first tank in the S4, 330 from the second... think I calmed down a bit after a week!)
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  13. rum4mo
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    rum4mo Active Member

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    [Mar 22, 2014]
    "Agreed, totally. Apologies for pulling the thread off course! (220miles from my first tank in the S4, 330 from the second... think I calmed down a bit after a week!)"

    I bought my car with "half a tank" - but after driving it home (55 miles), it asked for fuel next morning, it think that was more down to the way the fuel indicator "sits" and me believing that I had half a tank as told by the garage. Yes 330 is more like when I refuel - anyway, does your rev counter have a back light under the S4 logo?
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  14. benjie
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    benjie Active Member

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    [Mar 22, 2014]
    No it doesn't- noticed that almost immediately. Weird not to I think.
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  15. rum4mo
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    rum4mo Active Member

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    [Mar 22, 2014]
    benjie, thanks for confirming that, even if it is not what I wanted to hear, you seem to be agreeing with anyone else I've asked. So maybe time to accept that mine has not just become faulty! Thing is, why has it taken me since July last year to notice that??
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  16. allanmb
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    allanmb Member

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    [Mar 22, 2014]
    Steering the discussion back on topic ;-)

    What I am hearing is subjective views regarding revs and efficiency. I assume nobody has any facts regarding this?
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  17. Liquidfusion
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    Liquidfusion Active Member

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    [Mar 22, 2014]
    It depends on the engine size, for me I'm comfortable driving in gear 3 at 30mph, 4th gear at 40mph and so on

    If you feel your car struggling it's time to change gears, higher gear at low speed isn't always best as it may not be the optimum gear
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  18. allanmb
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    allanmb Member

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    [Mar 22, 2014]
    I think you are missing my point. I want to know what is the optimal revs for fuel efficiency, not what people choose out of habit /feeling /experience.
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  19. rum4mo
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    rum4mo Active Member

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    [Mar 22, 2014]
    I'm guessing that you should be asking this question while specifically making reference to an individual engine, it should really depend on TFSI or TDI also engine size and FWD or AWD and Man Trans or Auto Trans - though VAG seem to have this idea that fitting an annoying "change gear" thing that prefers a max of 2000RPM is a bit annoying!
    #18
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