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Octane

Discussion in 'A3/S3 Forum (8L Chassis)' started by Alais DJA, Mar 10, 2012.

  1. Alais DJA
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    Alais DJA Member

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    [Mar 10, 2012]
    I've been running 99 Momentum in the Audi since i owned it....

    The only real options you have are:

    97 = BP Ultimate

    98 = Shell V-Power

    99 = Momentum

    Thing is, Tesco in all their wisdom have extremely dodgy pumps. I wont go into how i "proved it " to them....but i decided to put 1/2 tank of Ultimate...

    The car genuinly feels more powerful, and i rang previous owner ( as we still speak ) and he said he only ever put BP ultimate in it.....

    Is it possible that a car can remember?
    #1
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  3. S3featesV9
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    S3featesV9 Active Member

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    [Mar 10, 2012]
    No I doubt it. How can a car remember what fuel it's been using?
    #2
  4. Pedrosousa
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    Pedrosousa Member

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    [Mar 10, 2012]
    Knock control could have some kind of adaptive values....
    #3
  5. TDIQ
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    TDIQ 8L > 8P > 8V

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    [Mar 10, 2012]
    Why not? They're meant to be tested on a yearly basis so I doubt they're "dodgy"
    #4
  6. Gops
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    Gops 6th gear @7000rpm

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    [Mar 10, 2012]
    Shell V power is 99 isnt it? I think optimax was 98 until they changed it. But i use V-power and when its not available i use tesco 99. Never use BP, car hates it for some reason.
    #5
  7. Jimgrim77
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    Jimgrim77 Member

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    [Mar 10, 2012]
    Shell v-power everytime for me.
    #6
  8. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 10, 2012]
    The ECU doen't remember it adapts... higher octane means less chance of detonation and less timing pull so the car will feel quicker..

    Shell V POwer is 99 octane, Tesco Momentum seems to contain something that leaves deposits on the plugs... I ran it for a while as its the only garage on the way to work when I use the S3 but after seeing all that **** on my plugs I am back on the V Power

    <tuffty/>
    #7
  9. Jimgrim77
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    Jimgrim77 Member

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    [Mar 10, 2012]
    Music to my ears that!
    #8
  10. SteveSAS
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    SteveSAS Member

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    [Mar 14, 2012]
    Mine is standard & I use Sainsburys Super which is 97 because its cheapest :thumbsup:
    #9
  11. Jimgrim77
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    Jimgrim77 Member

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    [Mar 14, 2012]
    You should only ever use the best fuel in these cars. Hiding to nothing if you don't.

    You don't see athletes eating fatty foods.
    #10
  12. vfr800
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    vfr800 Active Member

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    [Mar 14, 2012]
    I had a '95 1.8 A4 which loved Optimax - I could really notice the difference, my old A3 1.8T loved Optimax - but I had to rag it to notice the difference. My brand spanky new-old S3 - dunno yet I've only had it for a few weeks.

    Personally I like Optimax (V-Power). A few tanks fulls through the engine and my cars have always seemed to run better.

    My VFR800 VTEC will drink anything I put in the tank - but it's a Honda so will probably run on perfectly on any old cheap cr*p. =)

    Liam
    #11
  13. SteveSAS
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    SteveSAS Member

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    [Mar 14, 2012]
    Sainsbury Super is 97 and cheapest
    #12
  14. Paradox1
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    Paradox1 Active Member

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    [Mar 14, 2012]
    I use sainsburys aswell, its just gone up to 1.37 and v power is 1.44. Tbh my car don't like v power for some reason but runs perfect on Sainsburys
    #13
  15. rhubarb4
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    rhubarb4 Certified Jardo Slayer

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    [Mar 14, 2012]
    Iv been running Tesco Momentum for a year or so now Paul not had any problems, actually seemed to run better than on V power not noticed any deposits either, do you definitely think its down to the fuel.

    Chris.
    #14
  16. damo.h
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    damo.h DVLA Say it's Black

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    [Mar 15, 2012]
    Another here for the V power club. Car feels to put the power down so much better. Can instantly tell when the wife fills up. As she will throw anything in :banghead:
    #15
  17. Gops
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    Gops 6th gear @7000rpm

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    [Mar 15, 2012]
    Ban her! Or train her! You cannot allow this to happen. Next thing you know it'll have diesel in the tank and a "oops I picked the wrong one up"
    #16
  18. damo.h
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    damo.h DVLA Say it's Black

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    [Mar 15, 2012]
    oh mate believe me I try, and only I usually fill the car up nowadays... Cant teach an old dog new tricks as the saying goes ;)
    #17
  19. RyanS3TT
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    RyanS3TT Member

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    [Mar 15, 2012]
    I use tesco momentum in mine, as I seem to always get 5p-15p off per litre from a friend :)...

    Spark plugs get changed every 5k anyway as im a service freak.

    As for fuelling.. Probally a question for Paul.. If driving Sensibly (as I do on the work run) Rarely over 3k using cruise control (Currently getting 37mpg)...

    Is Cheaper fuel an option? - or to stick with the higher octane stuff.

    All about cost saving me.. typical in my job.
    #18
  20. Reload
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    Reload Bird is the Word!

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    [Mar 15, 2012]
    Not just cost saving mate, your car would definitely not be running to it's full potential on 95 so why use it? (Not sure if my mpg is any better on the good stuff though)
    #19
  21. Alais DJA
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    Alais DJA Member

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    [Mar 15, 2012]
    It's the CLASSIC scenario.

    Why even consider using cheap fuel to to save 50p!

    I had to be "moved on" by security at Tesco at christmas because a complete moron, was filling up his R8, with 95!!!!!

    If you cant run em properly, just sell it and get a Corsa
    #20
  22. Welly
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    Welly VX220 SC Driver :)

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    [Mar 15, 2012]
    Same here, Momentum whereever possible and no plug issues here. There was a spate of Tesco 99 having too much silica in it, which shagged some peopel's lambda sensors - maybe remnants of that?

    Why? It's hardly like running 95 RON is going to damage the engine to be fair. The engine will just adapt to what fuel it uses so that seems a bit daft IMO.

    How do you know he wasn't going to get home and bung an Octane booster in the tank to take it up to 100 RON.

    Or maybe he ran WMI and had 110+ octane? lol
    #21
  23. Alais DJA
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    Alais DJA Member

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    [Mar 15, 2012]
    So...

    Engines do adapt and remember the fuel they use?
    #22
  24. <tuffty/>
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    <tuffty/> Badger 5 Edition Staff Member Moderator

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    [Mar 15, 2012]
    The ECU adapts/reacts to the situations that the lower octane fuel bring up... lower octane fuel will increase the potential for timing pull so the ECU will detect this and pull timing as it occurs... std maps are tuned to fall somewhere inbetween so that if used on high octane fuel then timing will normally be pulled only on extreme circumstances but allow the use of lower octane fuel as it is within the range of the ECU ability to pull timing...

    Once mapped however the maps are designed for power and therefore higher octane fuel... running lower octane fuel on a remap will normally pull more timing than std and will be more noticeable as a performance drop when compared to the std map...

    The ECU remembers fuel adaptions to compensate for air leaks etc...

    <tuffty/>
    #23
  25. Welly
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    Welly VX220 SC Driver :)

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    [Mar 15, 2012]
    They don't remember. They adapt. Different things.

    If someone cut off one of your legs, you would adapt to using just 1. That's different to remembering.

    Changes in knock readings from the cylinders define how much timing is added or taken away. Less knock and more timing will be added, giving you additional power.

    The higher the octane, the better and cleaner the burn from the fuel. The better and more efficient the ECU will see this from the reduced CFs from the knock sensors, and will slap a bit more timing in. Lower octane fuel will produce the reverse effect.
    #24
  26. Reload
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    Reload Bird is the Word!

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    [Mar 15, 2012]
    Yes, after a couple of tanks the ecu will adapt the knock sensor to take advantage of the higher octane fuel. A couple of tanks of 95 and it will adapt back to that, with potentially, depending on the engine, a loss of power. It would not, however, 'remember' in the sense you mean, it will merely adapt as necessary
    #25
  27. Welly
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    Welly VX220 SC Driver :)

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    [Mar 15, 2012]
    Which tends to be more of a hindrance than a help! lol
    #26
  28. Reload
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    Reload Bird is the Word!

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    [Mar 15, 2012]
    Beaten to it by welly. In my defence I am in Kenya atm :rolleyes:
    #27
  29. Welly
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    Welly VX220 SC Driver :)

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    [Mar 15, 2012]
    And as such, reload is a very apt name.... lol. :thumbsup:
    #28
  30. Alais DJA
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    Alais DJA Member

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    [Mar 15, 2012]
    very good
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