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Fuel & Octane

Discussion in 'Homeowner Assistance Forum' started by CSpackler, Apr 25, 2010.

  1. CSpackler

    CSpackler LawnSite Member
    from NJ
    Messages: 14

    I apologize if this has already been answered elsewhere here. I actually emailed these questions to several major oil companies and they could not answer them, but these are questions about gas as it pertains to two stroke engines. Does gas degrade over time? If so, how much over what period of time? Does octane degrade over time? If so, how much over what period of time? Do fuel stabilizers work? How will degradation of fuel or octane effect two stroke and even four stroke engines?
  2. cgaengineer

    cgaengineer LawnSite Fanatic
    Messages: 15,778

    Fuel does degrade over time. How much? It depends on how well it is stored. If you keep the tank full it should last about 1 year without any trouble. The less air in the tank the better. I have had fuel in my generator for over a year and it still smells fresh and it still runs my machine.

    I have never used a fuel stabilizer because I rarely leave a fuel tank full of fuel with the exception of my generator, but I do not use stabilizer in it either.
  3. AI Inc

    AI Inc LawnSite Fanatic
    Messages: 27,009

    I have reaD THAT IT WILL BREAKDOWN WITHIN 30 DAYS. I have had problems with it in both my bike and my boat.
  4. cgaengineer

    cgaengineer LawnSite Fanatic
    Messages: 15,778

    I would say temperature and storing conditions play a large part in how long it lasts. Fluctuations in temperatures cause condensation which is why I suggest storing equipment with tank full to eliminate as much air as possible. Here in GA I have not had problems storing for over a year, but if I know it will be stored for a long time I will drain the float bowl prior to storing. This almost eliminates starting and carb problems at next use.

    No doubt in my mind that it starts breaking down as soon as it leaves the refinery, but how much I have no idea.
    Posted via Mobile Device
  5. KarlP

    KarlP LawnSite Member
    from MA
    Messages: 31

    The problem is either gas evaporating in the carbs and leaving all the residue behind or ethanol in the "gas" attracting water. I never add stabilizer to my snowblower, lawnmower, motorcycle, generator, or outboard but I do turn off the petcock and run all the gas out of the carb at the end of the season. Never had a problem doing that.

    As far as the ethanol goes, you can either get gas cans that seal really well and hope for the best OR donate a few $100M to your own lobbyists to fight the corn lobbyists are are sticking us with this horrible fuel.
  6. cgaengineer

    cgaengineer LawnSite Fanatic
    Messages: 15,778

    Or you could do what everyone else does and add Seafoam which contains more alcohol...what a great idea!

    I have never had problem draining float bowls so I will continue doing that myself and not play into the fuel stabilizer and additive industry.
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  7. betmr

    betmr LawnSite Bronze Member
    Messages: 1,663

    Gasoline turns to Varnish over time. This Varnish, gums up the small ports, screens and passages in the Carburetor, as well as helping to clog fuel filters. Today's small engines are not really compatible with Oxygenated (Ethanol) fuels. As well as attracting corrosion causing moisture out of the air, the Ethanol in today's Gasoline is suspected of having adverse effects on Gaskets, rubber, and plastic parts associated with small engines. Fuel Stabilizers, in my opinion, do prolong the longevity of fuel, but are not a cure all.

    When I prep my equipment for long term storage, I drain all the fuel, and run them till they are empty. I put a small amount of stabilized fuel in, and run them empty, again. By doing this, any small amount of gas that remains, is treated. I then add a teaspoon of motor oil in the spark plug hole, turn it over a few times to distribute on the cylinder walls, set the piston at top dead center (A moot point in a twin), and put the plug back in.

    As many Carburetor's as I've had to dismantle, clean and rebuild, I never leave a stored piece of equipment with fuel in it.
  8. Nosmo

    Nosmo LawnSite Bronze Member
    Messages: 1,216

    I use Stabil in my gasoline for the mower during the period it is in storage. I have not had a problem with the gasoline going bad during the time the mower is sitting idle.

    For my 2-cycle trimmers I use 40-1 mixture and late in the season I add a little bit of Stabil. For my Stihl chainsaws which use 50-1 I use Stihl 2-cycle oil which has a stabilizer added to it from the manufacturer.

  9. cgaengineer

    cgaengineer LawnSite Fanatic
    Messages: 15,778

    I don't doubt the effects of alcohol in a fuel system. In my years growing up I raced karts that ran on 100 percent methanol, if you didn't run gasoline through them after racing and drain the oil and replace with fresh oil the steel gas tanks would rust and the aluminum parts would corrode. If stored without prepping the oil would turn all white and milky from the methanol. I am sure ethanol causes corrosion, but I suspect at only 10 percent that this is minimal but it still happens. If you insist on storing with fuel in the system your best bet is to store with a full tank. Stabilizers may help, I just don't use them. Around here we have about 2-3 months of really cold temps where a piece of equipment may sit, for me it easier to leave fuel in the equipment and just start them from time to time.
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  10. CSpackler

    CSpackler LawnSite Member
    from NJ
    Messages: 14

    Here is what one oil company wrote in an email response to these questions:
    (Company Name) gasolines are manufactured to meet ASTM D4814 Standard Specifications for Automotive Spark-Ignition Engine Fuel. We sell fuel for automotive use and for all other uses such as marine, lawn mower, blower, weed whacker, all two cycle, etc. we recommend you consult your owners manual. Thank you for writing.

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