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Best gas for outboard

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  • Best gas for outboard

    I have been thining of what is the best gas for my outboard. The tag says to use gas with 89 octane rating. Mixed at 50/1 Locally I can get 3 grades of fuel. Reg. 87 mid grade 89 premium 92 to 93. My question comes up from checking out the way fuels sell. The fast seller is 87. The next is the premium. The slowest seller at a station is the mid grade 89 octane. I have always heard that fuel will loose octane sitting. If the mid grade moves the slowest than how much loss has there been? My thoughts are would you be better off mixing the 87 & 92 octane so that you would have a fresher fuel? Cost would average out about the same. What are others oppions?

  • #2
    Re: Best gas for outboard

    What make, model and year is your outboard, GR?Many of those labels refer to the technology of the time they were built. Gas has changed a lot in recent years.Almost all modern 2 stroke outboards run best on 87 octane unleaded. Most modern EFI 4 strokes can benefit from higher octane. If you have concerns about the gas aging, add Stabil to each tank.(239)


    • #3
      Re: Best gas for outboard

      I have a 1972 Mercury 140 Horse inline 6 cyl. I even wondered about running premium, but had thoughts of it carboning up.


      • #4
        Sign up today
        Re: Best gas for outboard

        My '02 owners manual says use a minimum of fresh 87 octane (R+M/2). I thought about running premium also, but I asked several filling station operators how much premium they sell and they said not much. Now you'd think there wouldn't be much evaporation of the more violatile particles that make up the higher octane fuel, in a quasi sealed tank buried in the ground at 55 degrees, but who knows. So I run the gas that moves the fastest....87.Mark
        If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.