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Running 91octane

Discussion in 'General' started by crazykiwiguy, Mar 21, 2020.

  1. crazykiwiguy

    crazykiwiguy New Member

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    Ive been running 91 octane petrol with fuel system cleaner through my 2005 vz commodore. Do you guys reccommend doing this for fuel economy? Yesterday I left home with 900kms left til empty on the dash. Drove 70km with the cruise control on and admittedly had the aircon going. Got home with 760km left til empty. Surely the aircon wouldnt use that much extra petrol or could it be the low octane petrol? The reason why I'm asking is I'm planning a road trip with not many petrol stations along the way. What does everyone think?
     
  2. vc commodore

    vc commodore Well-Known Member

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    Me personally I wouldn't run 91 as it is crappy.....Whether it has a baring on fuel consumption I don't know....Reason I don't know is, I have an earlier model car and run 95 and don't really keep an eye on consumption as such. I also found when I ran 91 once, the car ran like a pig.....Pinging etc etc...

    This is my opinion so we will see what others think
     
  3. krusing

    krusing Well-Known Member

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    The Average for that series is 600 > 660km per tank,
    Where your system hand not reset correctly.

    Its like when you disconnect the battery and to work on your car, and reconnect it,
    Its shows 999 k/m till empty, until it recalibrates to what is in the tank, the engine speed, and the vehicle speed.
    I always reset mine after I have filled up, and then check after a couple of minutes [ie: sitting at a set of lights]
    I would say, you will get similar to what my VY gets, an average of 8.2 > 8.9 L/Per 100k/m, on highways and open road.
    and average of 12 > 16 L/Per 100k/m around town, this also depends upon driving techniques,
    If my wife is driving, she can pull 12L/Per 100k/m, :rolleyes:
    But when I get in it, its a bit different, I like to drive it my way, and so the L/Per 100k/m increase a bit,
    Its not like I thrash it, I just like to have a bit of fun with it, and blow the cobwebs out, so to speak ;)
    this also depends with the road conditions, whether is -
    • straight,
    • winding,
    • overtaking,
    • hills
    • and the amount of towns you have to pass through and slow down too.
    The Air Conditioning can use up to 15% of power, depending how hard its working.

    PS: I did use E10 in VY at one stage, but heard some rumours it can do more harm than good to the fuel system, so I always run 91RON in the Super6.
     
    Last edited: Mar 21, 2020
  4. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    A simple theory, if the car manufacturing engineering team who developed the car say use 91 then use it, if they say 95-98 use it, if they say E10-E85 use it they designed it to run on that fuel. Higher the octane harder it is to burn than lower octane, it wont hurt the engine that's what the knock sensor is there for to pull back the timing.
     
  5. losh1971

    losh1971 Well-Known Member

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    I tested a number of fuels over a period and Caltex 95 and 98 came up as best economy over all other fuels. I now pretty much always use Caltex 95. I rarely use 98 as I didn't see enough improvement over 95 to spend an extra 6cpl above 95. Cost wise 95 is not as cheap as it used to be 10 years ago, when it was only 6-8cpl more than 91, now it's 14cpl extra.
     
  6. crazykiwiguy

    crazykiwiguy New Member

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    600kms on the open road? Or is that around town?
     
  7. krusing

    krusing Well-Known Member

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    600 > 660 k/m per tank on the open road with 91 on cruise control.
    I'm talking about my Super6 being a 75 Litre Tank

    Side Note: The Super6's run fairly efficient when driven correctly, as we have had ours 15 years so you know how to achieve the best economy.
    EG: Home to Mildura = 567 k/m and still have 1/4 tank left, which almost equates to approx. 100 k/m till empty.
     
    Last edited: Mar 21, 2020
  8. mechanic

    mechanic Active Member

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    Nope. nothing to do with how hard it is to burn.
    Octane indicates a fuels resistance to pre ignition.
     
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  9. Crowny

    Crowny Member

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    Depending on the sort of terrain and whether the driving is mostly highway or a bit stop start a range of 900km is doable but if there weren't many petrol stations around I wouldn't plan on driving 900kms and risk getting stranded. 900kms is certainly doable as today I went on a drive with highway driving and not much traffic. I got about 500kms from half a tank (2006 VZ Executive) and the distance to empty read about 440km. In a VY I have got 1000kms from a tank. However todays driving was in mostly flat country. There were only a couple of hills. I had about 3/4 of a tank of 91 octane last night and topped up with 98 octane today.
     
  10. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    Nothing to do with what? I think your adding on words I never said.

    Like I said higher the octane gives it a higher resistance and preventing early pre ignition before the spark plug ignites it , therefore harder to ignite than 91.
     
    Last edited: Mar 21, 2020
  11. tml678

    tml678 Well-Known Member

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    Well no..to be fair, you actually said this:

    You never mentioned a thing about higher resistance and preventing early pre-ignition in your first post....so someone is adding words on but it's not the person who quoted you..
     
  12. krusing

    krusing Well-Known Member

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    That sounds great to achieve that economy, but I wouldn’t risk it either trying to squeeze 900k/s from a tank, where I would aim for probably say average of 700k/m from a tank, for piece of mind, as mentioned that does depend on the terrain and towns to slow down through,
    I guess you could almost achieve the maximum economy if you were travelling across the Nullarbor.
     
  13. mechanic

    mechanic Active Member

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    You said nothing of the sort.

    Maybe it was the voices in your head?
     
  14. Trevor loves holden.

    Trevor loves holden. Well-Known Member

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    OMG.
     
  15. gossie

    gossie Well-Known Member

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    I run mine on 91 because that's what The General built the engine to run on PROPERLY, and would NEVER let the tank get much below 1/2 way down.
     
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  16. crazykiwiguy

    crazykiwiguy New Member

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    Thanks everyone. I'll let you all know how I go
     
  17. Drawnnite

    Drawnnite Obviously Unsensible

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    The distance to empty is like a magical being. it does a lot of calcs and other things to figure out amounts and values.

    Best option, do it the old school way. When you feel up, fill up to the top and that same point each time.
    check how many kms you've travelled and do the manual calcs.

    For example my SS will say x amount of distance to empty and average of say another amount.
    When depending on the travels will actually be different to doing the actual maths.
    IE computer says 12.3L/100 and Distance may be 400km to empty.
    When in reality its more like 10L/100 and 500km to empty when i've filled up
     
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