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  1. #1
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    Fuel-high octane vs. low octane

    What grade fuel do you run through your motor? I've heard those who run a low octane fuel called idiots by those who only run high octane fuel. But I have also heard that high octane fuel is not necessary and can damage your motor. What do you guys think?

  2. #2
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    RE: Fuel-high octane vs. low octane

    I run an Evenrude 150 DIHO and the book calls for unleaded regular. Which I guess would be the low octane you refer to. These new motors are computer controlled and I'm sure the mfg engineers know what is best for them. The hi test fuel not only cost more but very well may burn your valves. I'm not sure it will void a warrenty but thats something you should check out.....


    Don

  3. #3
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    RE: Fuel-high octane vs. low octane

    gator,

    I've a 2002 Merc 225 opti max. It calls for 89 octane gasoline. I've read that higher octane can shorten the life of the motor. As a result, I run 89. sometimes, if it has been a long while since I refueled, I may add a little higher octane to what is already in my tank.

    Good luck,

    Danny

  4. #4
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    RE: Fuel-high octane vs. low octane

    >What grade fuel do you run
    >through your motor? I've
    >heard those who run a
    >low octane fuel called idiots
    >by those who only run
    >high octane fuel. But
    >I have also heard that
    >high octane fuel is not
    >necessary and can damage your
    >motor. What do you
    >guys think?

    I HAVE 96 EVINRUDE 200 VINDICATOR. I RUN 87 OCTANE, BUT I ALSO RUN STABILIZER YEAR AROUND. NEVER HAD ANY PROBLEMS.


  5. #5
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    RE: Fuel-high octane vs. low octane

    low octane fuel ,when it is ignighted has has a slower burn to it so the fire last longer and that makes more heat compared to higher octane that burns faster,so there is less heat, that makes your engine run cooler, that is why they will perform better. i dont know about the cumputers and if they can tell the differences in octane . the carb run engines are better off with high octane. and good oil.and cold plugs. my thoughts... jon hoover

  6. #6
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    RE: Fuel-high octane vs. low octane

    I have a 95 Evinrude 225 Vindicator. All of the professional marine mechanics I have spoken with say high octane is best. I only use Chevron with Techron. From what I have been told, Not only does the H/O burn quicker and cooler but also cleaner.
    I always run fuel additive (Ring Free). In the past, I have run lower octane, and had problems, especially carbon buildup. Also from what I have read, The real problem with fuel and outboards these days is RFG gas which is said to corrode rubber fuel lines and parts.
    Of course What the heck do I know.
    Just my 2 cents
    Chefdave

  7. #7
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    RE: Fuel-high octane vs. low octane

    I agree with half of what Lawnman said the lower octane does burn hotter but it helps burn the carbon deposits off. That is why high octane fuel has so much detergent added to it.

  8. #8
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    RE: Fuel-high octane vs. low octane

    Gator, are you confused now==========

  9. #9
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    RE: Fuel-high octane vs. low octane

    Octane is the rating in which fuel ignites under pressure. The only reason to use high octane fuel is if you have a high-compression (racing) engine that when low octane fuel is used you have pre-ignition or pinging. When an engines pings not only is it not performing well but it can damage the valves.

    If you don't have a high compression engine you are throwing your money away paying for high-octane fuel. The best bet is to go with what your owners manual calls for. I have a 135 hp Optimax and it calls for 87 octane just like my Chevy Silverado.

    kc

  10. #10
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    RE: Fuel-high octane vs. low octane

    High octane burns SLOWER than low octane fuel. The reason currnet manufacturers advise the user to go with lower octane fuels is to REDUCE cabon buildup, a by product of combustion. Low octane fuel burns faster and more complete than high octane fuel, therefore there is less carbon build up. The engines today are "mapped" to use the low octane fuel. if you use high octane on a stock engine, you will get carbon buildup which can lead to engine failure after extended use.
    Bill Day



  11. #11
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    RE: Fuel-high octane vs. low octane

    My 2 cents....burn what the manufacturer recommends. I run a 10 year old Merc 150 XRI on 87 octane. It runs great and does what I need it to do. Never a problem with it.

    Good luck

    Rich

  12. #12
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    RE: Fuel-high octane vs. low octane

    i've got an older motor, '87 was told by mechanic to run high octane. when i use 87 octane my boat won't hardly run. really sluggish. was told with older models it was recommended to run higher octane

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