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Thread: Unleaded or Premium

  1. #21
    Join Date
    Mar 2012
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    Premium Fuel

    I ran comparisons with both Standard & Premium fuel in a 200HP Suzuki fitted to a Hooker 6.7 WRC. In near identical conditions the WOT speed & fuel consumption was better with the Premium. Hoe shot performance was also noticeably improved. Over-all after the trial I continued to use premium fuel

  2. #22
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    Sep 2012
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    11,090
    Quote Originally Posted by Slunnie View Post
    You can run more compression, more ignition advance and it will burn better at higher RPM - I don't think any of these will apply to the boat.
    although you can run more compression, engines are static in their compression ratio. the more ignition advance is the main benefit, if the engine allows it.

    i think they also burn cooler as the is less waste. not 100% sure on that though.
    Quote Originally Posted by DazzaTD5 View Post
    Its a land Rover Defender... you need a real mechanic

  3. #23
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    Jul 2012
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    Hobart Tasmania
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    159

    Octane fuel

    We had a marine engine specialist at our fishing meeting the other night and his recommendation was just to use normal 91 octane petrol for all outboards.

    Peter.

  4. #24
    Join Date
    Jan 1970
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    20,891
    I thought most Australian engines were tuned to accept 91, unless otherwise stated, so there was no advantage in going to a higher octane fuel.
    It's not scientific, but I have experimented with our 1.5 litre Mazda 2 on 91, E10 94 and premium and I didn't notice any advantage from premium, either in performance or fuel economy. Not scientific, just real world, of course.
    2009 Defender 110 2.4. ARB bulbar, Ironman winch, Safari snorkel, Steinbauer chip, AP HD clutch, Lightforce spots, larger tank, Off Road Systems drawer, Traxide 160 controller, Tekonsha brakes, Mulgo seat runners, Uniden UHF, Nuggetstuff seat corners, breathers, Polaris GPS.

  5. #25
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    Jan 1970
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    Avoca Beach
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    11,989
    Just to clarify, if a motor is tuned for 98 octane eg say a Golf Gti the it will perform better on 98 than on 95 or 91.
    AFAIK the main reason for this is that the ECU advance is tailored to 98 octane.

    The knock sensors on most modern motors retard the ignition advance in stages if knock is detected as is the case with lower octane grades. Some people notice a rattle at first while accelerating with lower octane fuel , then nothing as the ECU retards the ignition advance.

    If a car engine is tuned to 91 octane as with most "run of the mill" Japanese cars , then there is no advantage in running higher octane fuel , other that the effects of a lighter wallet.

    European fuel standard is 95 octane , vs Japan and Australia at 91, so most "run of the mill" European cars will benefit a bit by using 95. Although seeing E10 is now advertised as 94 octane then the effect should be pretty minimal for 94vs 95.
    If an outboard was tuned to 98 then it would be an advantage to use 98 , but I doubt very much whether outboards are tuned to 98 or that they have knock sensors. The Honda Jazz engine is tuned to 91 octane and it is the same engine as used in the Honda 115Hp? outboard.

    Regards Philip A

  6. #26
    Join Date
    Sep 2009
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    Brisbane
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    Wouldn't recommend running a car that requires 95 octane on a lower octane fuel.

  7. #27
    Join Date
    Jan 1970
    Location
    Central West NSW
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    11,760
    Quote Originally Posted by Eevo View Post
    although you can run more compression, engines are static in their compression ratio. the more ignition advance is the main benefit, if the engine allows it.
    Not all engines are static in their compression ratio, although that one probably is. Hi octane is about ignition resistance, which is why increased compression ratios as the fuel will tolerate increased temperatures prior to flashing. A high compression motor is more efficient, however you may use that efficiency. The reason ignition spark is advanced is just because its harder to ignite and so it is advanced to where it is purely to make the engine run properly. The end result internally to the engine with regards to ignition timing is similar irrespective of what combination of octane and compression.
    Cheers
    Slunnie


    ~ Discovery II "Storm" ~ ~ Series IIa 6cyl ute ~ ~ Series II V8 ute ~

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