stihl fs 90r

Discussion in 'Lawn Mowing Equipment' started by THIESSENS TLC, Oct 6, 2012.

  1. GrassGuerilla

    GrassGuerilla LawnSite Bronze Member
    Posts: 1,437

    Little octane lesson here. The need for high octane is due to high compression. At the higher compression and the heat associated with it can cause pre-ignition (little bits of carbon on the piston or combustion chamber get glowing hot and light the fire instead of the spark plug) A condition where the fuel ignite early in the combustion stroke. You see, the lower the octane, the easier it ignites. A higher octane rating is slightly more difficult to ignite. You want to use the lowest octane recommended. If it says 87, 93 will not help at all. Actually makes it harder to ignite. Additional octane beyond what is specified is actually counter productive. It's not going to cause problems (unless we get extreme). But it's simply wasted money.
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  2. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Posts: 13,286

    All the major brands specifically recommend using a minimum of 89 or higher octane in their equipment these days.

    This is lifted right from the manual for the Stihl BR600M-

    "Use mid-grade unleaded gasoline with a minimum octane rating of 89 (R+M2) and no more than 10 percent alcohol content.

    Fuel with a lower octane rating may increase engine operating temperatures. This in turn, increases the risk of piston seizure and damage to the engine."
     
    Last edited: Apr 13, 2013
  3. THIESSENS TLC

    THIESSENS TLC LawnSite Senior Member
    Posts: 759

    Well, I'll tell ya's...I will be runnin whatever octane it calls for. Engineers knows best! My buddies dad has the 90KM and says the tiller attachment works awesome! It actually pulls him, and he's about 200lbs. Says it has tons of power, so I'm thinkin the 110KM will have plently....
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  4. Ridin' Green

    Ridin' Green LawnSite Fanatic
    Male, from Michigan
    Posts: 13,286

    I'm sure it will. I was just throwing it out there in case you have, or think you might get into some ROW work, or heavy growth ditches.

    BTW, all my Stihl manuals say the same thing as the BR600 manual, and so do my Husqvarna and Jonsered's.
     
  5. Grassmechanic

    Grassmechanic LawnSite Silver Member
    Posts: 2,697

    the 110 will have plenty of power. I use my kombi with an extended hedge trimmer, saw, and edger, and always have plenty of power
     
  6. THIESSENS TLC

    THIESSENS TLC LawnSite Senior Member
    Posts: 759

    I honestly believe the 90KM will be plenty for what I use it for, but I think I might still get the 110KM just incase I get into some more heavier work. I don't think i'll need the 130KM...not yet anyways. lol
     
  7. aaronmg

    aaronmg LawnSite Senior Member
    Posts: 357

    Just bought the 90 km with the pole saw attachment.. didn't need the weedeater attachment just yet... I have a 323 husq. The dealer told me after 9-10 tank fill ups on the km 90 it will rise in power significantly??? as of now i'm a little skeptical? using 93 octane and the stihl mix on the 90 and reg 87 and generic oil on the husq. if i'm neglecting the husq. its 7 years old and wanna hear some opinions from the pros out there..
     
  8. Grassmechanic

    Grassmechanic LawnSite Silver Member
    Posts: 2,697

    yeah, the 4-mix engines have a little longer break-in period.
     
  9. aaronmg

    aaronmg LawnSite Senior Member
    Posts: 357

    my dealer also said the km110 might be discontinued? and my 90 won't get alot of work til next year should i break it in as fast as possible?
     
  10. weesa20

    weesa20 LawnSite Member
    Posts: 169

    Will the other attachments fit the 250? My dealer told me that they wouldn't fit- have an older 250 so maybe that has something to do with it
     

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