Echo PB-755...89 Octane???

Discussion in 'Lawn Mowing' started by dmanb2b, Oct 2, 2006.

  1. dmanb2b

    dmanb2b LawnSite Member
    Messages: 102

    Hi to the forum. Just picked up a PB755 and the manual calls for 89+ octane 50:1 you all run 87 octane succesfully....that what I run on my weedwacker and chainsaw:dizzy:

    CAROLINA MOWER LawnSite Member
    Messages: 6

    Yes, Use 89 Or Higher Oct In This Unit, 87 Will Run But Will Clog Your Muffler And Ports Faster And Build Carbon Up On Piston Head
  3. grass_cuttin_fool

    grass_cuttin_fool LawnSite Gold Member
    Messages: 3,526

    Ive asked several dealers when they have had an open house and factory reps there, and Ive even emailed stihl ( I use mainly stihl products) and no one has ever gave me a reason for 89 octane other than the book calls for it.

    That being said.......Ive always used 87 and had units run for years with it, this year I ran some 89 octane also and I saw no difference in preformance. 89 shouldnt have anything but more octane. There is no additional aditives or detergents between octane grades that im aware of, maybe between manufactures of gas, as each manufacturer has there own additive package.

    If anyone can tell me why 89 is recommended, I would like to know also.

  4. Jason Rose

    Jason Rose LawnSite Fanatic
    Messages: 5,858

    Many parts of the country (here at least) gas producers are "sneaking" ethanol into the low grade unleaded (the 87 octane), however usually the mid-grade, 89 or 90 octane, is 10% or so. Anything under like 6% and they don't have to report it being in there. My stihl blower runs like CRAP in the summer if I use mid or low grade in it. Has nothing to do with the octane IMO as mush reasearch has concluded that the octane rating of fuel really has no effect on how well a "standard" engine runs or performs. It's all to do with the Ethanol, which 2 strokes don't care for. Usually there is NO Ethanol in the "premium" fuel.
  5. grass_cuttin_fool

    grass_cuttin_fool LawnSite Gold Member
    Messages: 3,526

    Ive heard the same thing Jason, but then I had a gasoline dist tell me that ethanol is blended in all 3 octanes because of lower emissions in certain parts of the country.
    The gasoline dist actually told me what makes the most sense, when ethanol is blended with gas, the octane can drop a point or two. That is why they recommend 89, depending on how much ethanol is blended, it would still have a rating of 87 or more which is actually the lowest the engine manufactures recommend. But I cant get Stihl or Robin to confirm this

  6. tallimeca

    tallimeca LawnSite Bronze Member
    Messages: 1,229

    here is why.

    1) There is more detergent in the 89 then the 87. Keeps the engine cleaner and less carbon build up.

    2) With emissions clamping down, the engines are running hotter and leaner. Echo with the Tornado and power boost technology, Redmax with the strato charged technology. Running the less octane can lead to detonation. Basically a fuel's octane is it's ability to resist combustion. With 87, you can get the fuel igniting on hot spots on the piston and cylinder before the plug fires.

    I had a customer a couple years ago who was dealing with Stihl dealer who closed up. He came to me for service. All his engines were self destruction. 2 back pack blowers........all cracked piston skirts. Top of the cylinder looked like shot gun blast hit it. Detonation. He was using the cheap gas.

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