(Just a quick one!) High octane fuel?

Discussion in 'General Questions' started by Hajuu, Apr 18, 2010.

  1. Hajuu

    Hajuu Member

    Hey guys,

    I was just about to fill up my jerry can and I thought id ask if it was possible to use high octane fuel in one of these in conjunction with a really nice racing oil?

    Here we have regular (I think its 92 octane) medium (95 octane) and high (98 octane). It has a bit of extra 'premium fuel stuff in it too like everywhere I assume.

    Anyway, will using a medium run me any risk of siezing my engine (or worse)?

    Seems to me, that the main thing would be that itd burn much hotter, so would that mean more or less oil? (More I assume)

    Cheers for the input
    Hajuu
     

  2. chefdouglas

    chefdouglas Member

    higher octane will increase engine heat which is undesirable but will not give greater performance unless the engine is designed for it. My guess is if you went to a lower octane you would not notice a differenced. When the HT motor was designed leaded gas was still used at something like 78 octane. Thats not to say if your riding around on a 30(F) degree day it would make a difference.
     
  3. kerf

    kerf Guest

    Higher octane fuel doesn't run hotter or produce more power, it does have more resistance to the condition called detonation. This is the result of compression induced firing rather than spark induced firing. Running higher octane fuel, than required, won't effect anything other than your wallet.
     
  4. motorpsycho

    motorpsycho Active Member

    I couldn't agreemore with this statement.
    Unless you have a very high compression racing motor, running high octane fuel in a h.t. motor is just throwing your money out the exhaust pipe.
    these motors were designed to run on "regular" gas (92 octane or so)
     
  5. Gh0stRider

    Gh0stRider Banned

    I agree, considering their history, these generic chinese 2 strokes will run fine on poor quality fuel and high octane is just throwing money out the window. Buttttttt, I hear that premium fuel (at least here in the USA, and not in Hajuuland) is likely NOT to contain any ethanol. This is better for storage, as the gasahol (10% blend) that is sold as gasoline can suffer from "phase separation" when stored under certain conditions. This causes driveability issues and possible engine seizure with a 2 stroke. Just ask any outboard tech and he'll tell you all about it.
     
  6. kerf

    kerf Guest

    I honestly don't know. All the pumps I've seen, indicate 10% ethanol, never had an issue in my two strokes running regular or my 460 on premium.
     
  7. Gh0stRider

    Gh0stRider Banned

    Where I live, the regular unleaded pumps will indicate that the fuel will contain "up to" 10% ethanol. Some will even tell you outright that the fuel is 10% ethanol. The premium pumps have no such label. Even then, I am not 100% sure. You hear a lot of static on the intarwebs.
     
  8. Gh0stRider

    Gh0stRider Banned

    Oooooh - just caught the "460" reference. Those little engines can scream!
    Currently, I am working on a minimoto (cagliari or "cag") engine on a BMP friction drive kit. I bought the kit a few weeks back (scratch n' dent special) but haven't had the time to prep an engine or bicycle. Just ordered the engine, now I need to figure out an exhaust and a gas tank setup. The little cag motors are not nearly as good as the GP460's but they aren't too shabby. I hear that the cags need premium fuel too, especially when running a "rockit" key to advance ignition timing.
     
  9. Hajuu

    Hajuu Member

    Great, thanks guys.
     
  10. Fabian

    Fabian Well-Known Member

    Higher octane fuel does not produce more power in itself, it just lets you run more compression and resist the affects of detonation.

    It works by burning in a slower and more controllable way.
    You will notice an improvement in low and mid rpm torque.

    Fabian
     
  11. KCvale

    KCvale Motorized Bicycle Vendor

    Hmmm... Logic tells me running Premium especially for the extra rich gas/oil ratio during break-in would be best.
    It's not like we are talking a lot of money in cost per/mile.

    If crappy gas and an oil mix is all you need, why not just fill-up on diesel fuel?
     
  12. kerf

    kerf Guest

    A very interesting comment, please elaborate on that "logic".
     
  13. Karryhunt

    Karryhunt Member

    Yeah.....with about 95 percent of todays cars using regular gas, I avoid using premium due to the possibility of contamination from laying in the station tanks too long.:ack2:
     
  14. KCvale

    KCvale Motorized Bicycle Vendor

    Allow me to rephrase that...
    Instinct tells premium should be better, I am looking for the facts as to why it's not is all.
     
  15. Karryhunt

    Karryhunt Member

    See above post.
     
  16. kerf

    kerf Guest

    Fuel grade (octane requirement) is a function of compression ratio. If the manufacture recommends a fuel with a octane rating of 87, nothing will be gained running higher octane fuel. The "logic" that if it cost more, it must be better, doesn't always work. In any event, during the break in period, the engine will have lower compression.
     
  17. Gh0stRider

    Gh0stRider Banned

    Because diesel fuel is not the same as crappy gas and oil mix.
     
  18. Hajuu

    Hajuu Member

  19. kerf

    kerf Guest

    Seen it, I consider the people in this community to be living it. We're pretty much doing what those "daring early pioneers" did, except our machines are a little smaller.
     
  20. rm26x

    rm26x New Member

    another point to consider, premium fuel will have less if any ethanol like someone else stated, which dries out gaskets and seals in the carburetor. We like to run premium fuel in any small engine we repair at work. (I am a small engine mechanic by trade) The EPA is even trying to make it so all gasoline sold is 15% ethanol content, but the small engine manufactures are all trying to fight that as small engines will not run right on 15% ethanol blend and the ribber diaphragms used in the carbs for fuel pumps will not hold up to it along with other issues.

    When I get my 80cc 2 stroke kit, I am going to deck the head to raise compression to better match premium fuel. It will give me more bang for the buck, for little cost.
     
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