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Octane ? What do you put in your saw?

Post in 'The Gear' started by basswidow, Mar 5, 2010.

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  1. Kenster

    Kenster Minister of Fire

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    I just a got a new MS390. Haven't fired it up yet but I've started reading the manual. It clearly says to use hi octane gasoline.

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  2. Tony H

    Tony H New Member

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    the big advantage with av gas is not the high octane but the strict controls ment to prevent contamination and no alcohol is allowed.
    this also means the fuel does not "go bad" or start to break down quickly (60-90 days) like automotive gas.
    Planes are often stored or parked for longer times and would have much worse outcomes from a tank of old gas.

    Here is a good article that explains mogas and avgas octane and ethanol and other facts about gas from the folks at Shell

    http://www.shell.com/home/content/aviation/aeroshell/technical_talk/the_blue/issue_6_2007.html

    Here is a sentence that everyone should read from the shell paper.

    Octane rating is a measure of how resistant a fuel is to detonation; the higher the octane rating, the more the fuel / air mixture can be compressed without detonation happening. To make this clear, octane rating is not a measure of the amount energy in the fuel but is a measure of its resistance to detonation. The advantage or higher octane fuels is that a higher compression ratio or supercharging ratio can be used, which then leads to a higher volumetric efficiency within the engine, which in turn means more power output for a given fuel burn.


    I hear you guys with no non ethanol stations in the area . Closest one to me is 20 minutes away so I add stabil instead and it seems to help as I usually get 20 gallons of gas at a time for all the small engines and it will last me a couple of months and maybe longer in the winter. I also leave fuel in lawn mowers , boats , jet skis, snow blowers and anything else from season to season and since using stabil the last 20 plus years have never had a fuel related problem with any engine. I even had a Mazda RX7 that sat for 5 years with stabil treated fuel and it started and ran perfect !
  3. tiber

    tiber New Member

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    The 93 octane thing (or 91) is because the gas has much better formulation than the 80-series stuff. It doesn't give you more power, run cooler, whatever - it simply has less of a chance to break down and covers up timing problems in the engine due to load or wear.

    I run 93 to 102 octane in the MR2, I put the same thing in my chainsaw because I know it's never going to have an issue getting that stuff to touch off. Also the higher the octane, the less ethanol is in the gas. Ethanol is typically 75 to 80 octane, so 93 octane hardly has any.

    Also I put used motor oil in my chainsaw but that's a different topic.
  4. Redskins82

    Redskins82 Member

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    Thanks for the link. The last time I saw it posted there was no station within 20 miles of me. Now the list has changed and the second to the closest gas station to my house is listed. It's less than a mile away. Excellent!

    btw, I use nothing but 87 octane.
  5. Redskins82

    Redskins82 Member

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    Why delete my posts when you'll allow someone to peddle ignorance like this? People don't need to be given such erroneous information.


    "Starting with the 2007 Indy race season, the race vehicles will run on E100, 100 percent ethanol. Pure Ethanol (E100) has an octane rating of 113, as compared to straight gasoline which has an octane rating of 87 to 92."

    http://e85.whipnet.net/news/indy.ethanol.html

    "Ethanol is a high-octane fuel. Octane helps prevent engine knocking and is extremely important in engines designed to operate at a higher compression ratio, so they generate more power."

    http://www.afdc.energy.gov/afdc/ethanol/what_is.html

    "Pure ethanol (E100) fuel has a higher octane rating of 106 RON compared to gasoline’s 95 RON. Using a 12:1 compression ratio and twin turbochargers running at 1.0 bar boost, the Aero X BioPower engine delivers a hefty 143hp per liter displacement. Turbocharging with E100 fuel allows the use of a higher compression ratio—giving more engine power—than is possible with gasoline because of the risk of harmful knocking (pre-detonation)."

    http://www.greencarcongress.com/2006/02/gm_introduces_4.html

    "The CCX Edition runs on regular petrol and produces 888 Bhp, whilst the CCXR Edition has been modified as a bioflexfuel car, and can run E85, E100, regular 98 octane petrol (Europe) or a mixture of the three. When run solely on petrol, the engine produces 888 Bhp, but the higher octane E85 fuel makes higher compression, boost pressure and increased spark advance possible, enabling the engine to deliver a staggering 1018 Bhp."

    http://www.koenigseggedition.com/

    Do I need to post more links?
  6. tiber

    tiber New Member

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    Well, that's fine if you're buying your gas from NASCAR, but I believe the thread is about buying gas from the gas station. I don't think anyone is going to the ethanol station and filling up their chainsaw. Let me explain myself.

    There is no "standard formulation" of gasoline, or gasoline/ethanol blends. If you google for "what is gasoline" a recipe won't come up. A better discussion would be to compare who's gas (as in sunoco, exxon, whatever have you) seems to store best. We can only speak in the most general sense when it comes to arguing about who's gas has what in it.

    Now, where the higher octane = less ethanol metric comes from is the SCCA. After MTBE was made illegal, those of us who ran cars which needed it either had to turn the boost down or figure out who had the least ethanol. (Or apply for a permit, pffft) Problem being ethanol, when blended, is a great fuel, but our cars ran on gasoline. Would you put diesel in your engine? Kero? Fuel from the space shuttle? These might burn well, but the bottom line is they're different from gasoline the same way coal wouldn't burn well in a wood stove. The gas picks up water, eats the fuel lines, and frankly there's no difference between a "summer car" engine and your chainsaw except the chainsaw sees intermittent use all year round.

    Common sense arguments aside, I didn't want to plug a specific brand in my post, but since we're down to it - Sunoco Marine Super blend is known to have little to no ethanol and Sunoco GT runs ads specifically saying it also does not contain methanol.

    EDIT: Found the sunoco blend - 260GTX is what you need to use in the bracket which forbids ethanol. If you're looking for the 260GT blend (federal minimum for road use), you can find a station. If you want to go for the gold and buy nonstreetable gasoline, find a dealer.

    I really hope I don't come off sounding like a sunoco commercial, but they make good stuff.
  7. flewism

    flewism Member

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    I didn't read this hold thread, but I run 93 or better octane in my saws and boats, 87 in everything else. All small engines get stabil come fall, except the diesels.

    This is what works for me.
  8. Rich L

    Rich L Minister of Fire

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    If I recall correctly the Stihl manual says use 89 octane.That's what I use with no problems so far.
  9. Nonprophet

    Nonprophet Minister of Fire

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    Your post was probably deleted because it wasn't very nice--i.e. calling people "goobs" or whatever. I see by your post count that you're relatively new here, one thing you'll (hopefully) quickly learn is that for the most part people are very friendly and helpful here. Name-calling doesn't really fit in very well.

    NP
  10. smokinj

    smokinj Minister of Fire

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    To each is own I have a large investment in my saws and I will run 93 or better, it just makes me fill all warm and fuzzy!
  11. oldspark

    oldspark Guest

    Our regular unleaded is 87 octane and the gasahol is 89, just saying.
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