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Thread: Fuel discussion

  1. #1
    Supporting Member II Turbo Mopar Contributor
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    Fuel discussion

    A bit of science here what goes on here as I have worked as a gas chromatographer supporting the petro industry. First isooctane by definition has an "octane" rating of 100 and n-heptane is defined as zero as used in the refinery knock engines. If we used pure isoctane (or any other saturated/aromatic), the fuel will be stable "forever". Crude oil has a very small percentage of suitable saturated hydrocarbon so since the demand of gasoline is very high we need to create a suitable fuel from the remaining stock.
    Since most of the remaining stock is higher molecular weight we need to "chop" the molecules into usable pieces. This is called "cracking" best yields by Catalytic cracking. This is the Cat in the refinery. The cat works very well but produces a very large fraction of unsaturated hydrocarbons. It is these unsaturated hydrocarbons (aka olefins) that are unable and react over time to form gums and varnishes.
    Many different reactions are involved but it is well known that some chemicals can be added to slow these reactions down. This are the additives we are discussing
    Do they work? Yes but there are a few addition methods to help them even more
    In the refinery, the gasoline fraction from the cat is not only full of olefins but it is not high enough in "octane" for modern cars so we need to blend in high octane stock from elsewhere in the refinery. These other stocks can be created from upgrading the gasoline from the cat. Two of such stock is the alkylate or reformate. Both are high quality, high "octane" and highly stable. For example alkylate is very high in isooctane and reformate is very high in toluene. If your fuel was made from a blend of these very high quality products the fuel will very stable.
    Conclusion: Since the higher quality product are more expensive and higher "octane". the refineries will use as much cat gasoline as they possibility can and only use the higher quality products in quantities to meet the minimum octane rating. The high octane fuels will contain lower levels of the bad cat gasoline and thus be more stable. This discussion refers to NON ethanol based fuels. Some refineries use zero bad cat gasoline in their 91 and higher grade fuels. After learning this in the early 90's, I switched to 100% usage of 91 or better octane fuel. Zero fuel related issue on my cars, lawnmower, snowblower etc even without adding fuel stabilizer
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

  2. #2
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fuel discussion

    That is very interesting thanks for taking the time to post it up. What would you say the shelf life is for 93 octane that would power, let's say, a generator?

  3. #3
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    Re: Fuel discussion

    Hi Brian,
    This is complex but you want to avoid ethanol I would try this link
    https://www.pure-gas.org/
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

  4. #4
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fuel discussion

    Thanks. With the proliferation of propane powered units, I'm tempted to go that route, but if I can find a decent used unit which runs off of gas, that would be more than acceptable too.

  5. #5
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    Re: Fuel discussion

    Quote Originally Posted by cordes View Post
    Thanks. With the proliferation of propane powered units, I'm tempted to go that route, but if I can find a decent used unit which runs off of gas, that would be more than acceptable too.
    I wonder about the new "engineered" gasolines on the market designed for small engines. It is real pricey as I seen at home depot IIRC about $15 per gallion.
    https://trufuel50.com/4-cycle-mix/
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

  6. #6
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fuel discussion

    Wow, that stuff does it all!

  7. #7
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    Re: Fuel discussion

    Quote Originally Posted by cordes View Post
    Wow, that stuff does it all!
    Great comment Brian.....

    Likely they buy it tax free so tons of profit per can
    Regards,
    Miles

    DD '87 Sundance T1, 12PSI, SLH with rear disks
    '87 CSX #432

  8. #8
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Fuel discussion

    Quote Originally Posted by chromguy View Post
    Great comment Brian.....

    Likely they buy it tax free so tons of profit per can
    I didn't think of that, but I'm sure you're right. It's for off road use, so I'm sure they don't pay fuel tax on it. Profit indeed.

  9. #9
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    Re: Fuel discussion

    Regarding the engineered fuel for small engines... A friend years ago worked for Stihl and would get me their brand of 2-cycle fuel for my lawn equipment for dirt cheap. It works great & stores well in those metal containers. The odor of the fuel was pretty similar to the higher octane fuel from the station in town that sold 100, 110 & up octane fuel. Now that my supply of Stihl fuel dried up, I just pick up a gallon of 100 octane & mix in the oil each spring. I haven't had any issues with carbs or anything that other friends have regularly.

    Another acquaintance that works for the area fuel distributor has echoed similar info to what Miles shared. 91 octane without ethanol is usually the good stuff, 89 with 10% ethanol wasn't bad but definitely lower grade. A few years back we started getting 87 octane gas with up to 15% ethanol in it. He said that the base gasoline in that mix was the cheap garbage gas, usually 83ish octane and the ethanol was added to make it acceptable for general use.
    “If the people of the nation understood our banking and monetary system, I believe there would be a revolution before tomorrow morning.” -Henry Ford

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