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fuel octane

Discussion in 'Chainsaw' started by Vman, Oct 31, 2005.

  1. Vman

    Vman ArboristSite Operative

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    i have read in some of my owner's manuals that using a higher octane fuel in 2-strokes will keep the engines running cooler. so which should be run in the saws, blowers, and brushcutters for best performance and engine temp, 87,89, or 92? i usually use the stihl mix at 50:1, sometimes i use the echo mix.
    thanks
     
  2. computeruser

    computeruser Addicted to ArboristSite

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    I've always run 92. Never heard a good reason not to, and the prevailing wisdom is that higher = better. Since there is so little cost difference, I figure it can't hurt.
     
  3. Diesel JD

    Diesel JD AboristSite Guru

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    I've run all grades, I haven't seen a performance difference, but the Stihl manual calls for mid grade unleaded 89/90, so that's what I would use in a Stihl, or whatever the manual on your particular saw calls for.
     
  4. 12guns

    12guns ArboristSite Operative

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    I was told the higher octane burns cleaner...come to think of it, I'm not sure who told me that, but it makes sense to me. After putting 214,000 on my Tacoma, I wish I could tear the engine down and see if all that extra money was all for nothing!!
     
  5. Lawn Masters

    Lawn Masters Banned

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    I would love to see about that myself.

    IMO, this subject is a debate with no clear answer, theres people that say it is better to use high octane fuel, some say it isnt, and some, like me, prefer to just say use whatever you can afford to use, and keep fresh fuel.
     
  6. -e-

    -e- New Member

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    straight from Husqvarna support site:
    "Husqvarna recommends a fuel octane rating of 89 or higher with its engines. This will help prolong the life of maintenance items as well as the life of your engine. Also, higher octane gasoline burns cooler, cleaner and causes fewer emissions."
     
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  7. klickitatsacket

    klickitatsacket Banned

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  8. pinus

    pinus ArboristSite Operative

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    There is difference with different fuels. I use gasoline with 98 or 95 octane. The engine is working better with the 98 fuel. 95 here is in reality the fuel with unknown quality ;)
     
  9. Vman

    Vman ArboristSite Operative

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    can you or anyone explain why the engine runs cooler as stated in the manuals? i always use mid-grade, but just am curious to the "cooler running" statement that is in the manuals.
     
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  10. bvaught

    bvaught ArboristSite Operative

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    In your chainsaw you should run 89 octane or better to provide a detonation margin. You could run your saw on 87 all day long in many conditions and never notice a problem. But if you were running the saw hard (higher load is more likely to detonate or preignite), with a rich oil mixture (mix oil lowers octane), on a dry hot day it might detonate and ruin your saw. So.... spending a little extra money on premium gas just makes good sense.

    Now in your car..... you are a fool to run anything more than 87 octane fuel, unless you have problems with heavy spark knock (you really need a tune up), or you have some exotic car that is designed to take advantage of higher octane fuel.

    I just want to clarify that the above was written with respect to a "stock" saw.
     
    Last edited: Nov 1, 2005
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  11. timberwolf

    timberwolf Addicted to ArboristSite

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    On modified saws with increased compression higher octane is not just an option. A tuned pipe also stuffs more air/fuel in wich has much the same effect as a bit of increased compression.
     
  12. bwalker

    bwalker Resident Hack Sawbuilder Exposer

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    There is no such thing as " pre-detonation". There is Detonation and Pre-ignition. These events can be related, but are not always. In a nutshell pre-ignition is the mixture ignition before the sparkplug fires. it is often caused by a glowing carbon deposit or plug electrode. Detonation on the other hand occurs after the plug has fired. In a detonation event the plug ignites the mixture and it starts to combust as it normaly would. Just prior to complete combustion the remaing mixture violently explodes hammering the piston/head and releasing massive amounts of heat.
    As for octane. higher octane fuel does not burn cooler, or slower. This is a old wives tale and it matters not the Husky is technicaly wrong. The only way high octane fuel will cool a engine down is if you have one of the abnormal combustion events mentioned above occuring. With that said I always run the highest octane pump gas in all my two cycle equipment. its cheap insurance for a engine with very high piston temps like a two stroke.
    And dean, those pistons you pictured arent shat. Check this one out.
    Piston.
    http://www.arboristsite.com/attachment.php?attachmentid=4075
    Pipe painted with molten alluminum.
    http://www.arboristsite.com/attachment.php?attachmentid=4076
    Cracked pin boss.
    http://www.arboristsite.com/attachment.php?attachmentid=4080
     
  13. smcowboy1974

    smcowboy1974 ArboristSite Operative

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    I run 100LL av gas 50% with 50% 87 octane. I don't know if the lead in the 100LL does any good, but av gas doesn't get old like regular pump gas! I use Mobil racing 2T at 32:1 with 50% husky two cycle oil. Works for me!
     
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  14. Chris J.

    Chris J. Addicted to ArboristSite

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    From what I read here, a lot of you get the experimental gas when you buy 87 octane. Here in Houston our 87 is real gas, unless you buy it at RaceTrak (I suspect that they water down their gas, or buy inferior gas). I can't speak for saw wear & tear, but Shell 87 octane seems to be a step above other brands, at least in my Frontier 2.4 & Jetta 1.8T. It probably helps that Shell has a large refinery in Deer Park, very near Houston.
     
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  15. klickitatsacket

    klickitatsacket Banned

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    Ben, thank you for the correction. I tend to lump the 2 together. I notce that bearings are beat to crap as well with the pre-ignition and with detonation. Many times I find that detonated piston wear and embedded needle bearings on the crown of the piston will be present at the same time.
     
  16. 2Coilinveins

    2Coilinveins Former Member

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    That's odd KW, around here Shell gas is garbage that I wouldn't use for parts cleaner. Chevron gas seems to have higher octane than Union 76. Back when I had my Nova I'd tune to the edge using Chevron, and the same grade from Union 76 caused it to ping. None of my current vehicles care what they get. My F250 would probably burn diesel without complaint. I run premium in all my two stroke stuff.
     
  17. MotoBoyMatt

    MotoBoyMatt ArboristSite Member

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    Husky is technically right. High octane fuel has a lower heating value and will therefore provide less heat energy (ie burn cooler) in the same engine when compared with lower octane fuel.
     
  18. bwalker

    bwalker Resident Hack Sawbuilder Exposer

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    This is false. All gasoline has around the same BTU per gallon.

    I might also remind you guys that just because your buying gasoline form a Chevron or Shell station doesnt mean that it was refined by them. I once worked accross the street from a Mobil bulk terminal which recieved its gasoline from a BP/Amoco refinery in Indiana via pipeline. All sorts of tanker trucks filled up at this Terminal. Including Shell, Speedway, Mobil, Amoco and Citgo.
    Gasoline is a comodity and as such is traded all over the place regardless of brand.
     
  19. Vman

    Vman ArboristSite Operative

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    ok, you are on the right rack to answer my question, but i still cannot make sense of it. i would tend to think a higher octane fuel would be hotter, that is the part i cannot understand.
    is it possibly cause the higher/hotter combustion does more work for the engine, making the mechanical parts of the engine work with less of a load/friction (if u understand what i am saying, i know it sounds confusing)?
     
  20. bwalker

    bwalker Resident Hack Sawbuilder Exposer

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    Once again octane rating has nothign to do with the BTU's....
    If you would like I can provide some refferances.
     

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