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Shelf life of premix gas 50:1 ??

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  • Shelf life of premix gas 50:1 ??

    I kinda surfed around looking for an answer on shelf life on premixed 50:1. I have 2 tanks in my boat both of them are 6 gallon portable ones.Ones full and the other empty didnt get to use it all last time out (approx 2 weeks).Question is how long before the octane level drops and or the gas looses its bang? Thanks guy's..

  • #2
    Re: Shelf life of premix gas 50:1 ??

    2 weeks? I wouldn't worry about it.
    2002 20' Hydra-Sports 202DC 200HP Yamaha HPDI
    1976 18' Starcraft SuperSport 90HP Evinrude
    Restoration thread


    • #3
      Re: Shelf life of premix gas 50:1 ??

      I've used last seasons gas for 30 yrs. and all I do is shake well before using. Never had any damage. Of course this is with good quality oils, Amsoil, Quicksilver.


      • #4
        Re: Shelf life of premix gas 50:1 ??

        Okay no problem,I was just curious because it gets above the 100 degree mark again here in Arizona,even with the boat covered its hot.So I was wondering with all the good stuff evaporating the gas might not be all that good after a certain amount of time


        • #5
          Re: Shelf life of premix gas 50:1 ??

          Ask the marine shop..gas is gone in 30 days..Ethanol attracts water, read about how bad it is by googling it..I just gave away 100 gallons of gas left over in 4 boats I own...My motors are worth too much to me to have them destroy themselves from lack of octane.. While shaking the tank may work for Merc 850 my boats are not shakeable...lastly you can't make phase separated fuel come back to gether..Also I have a racor water separator on every boat I own due to the terrible fuel we are all stuck with. Again, stop by your local shop and see what the majority of reasons engine blow up from..Overheating problems or fuel problems i. e. carb jet or fuel injected getting clogged and causing that cylinder to blow due to lean conditons. The guys I hang with use their fuel in 30days or pump in out and take it too reclamation centers...$15000 motors aren't worth destroying for a couple of hundred in old gas...Again just my 02 but ask the pro's.........


          • #6
            Re: Shelf life of premix gas 50:1 ??

            Thanks Guy's I respect everyone's opinion on this matter. I figure I will just go ahead and use fresh fuel and use my old stuff for whatever (makes a good cleaner for greasy parts).Both motors I rebuilt had signs of running lean due to improper maintnance or lack of . I choose to go the easy route and the cheapest. @ $3.50 per gallon plus oil is alot cheaper than 2-3-4 hundred $$$ in parts plus down time. I really loved the expierence rebuilding my motors but I dont feel like doing it again because of my mistake/stupidity.


            • #7
              Re: Shelf life of premix gas 50:1 ??

              Good idea to use a stabilizer when you buy your fuel. Gas dies in about 30 days.


              • #8
                Re: Shelf life of premix gas 50:1 ??

                Gomer, You have touched a nerve with your question. Almost as much fun as an oil thread. Maybe you can start one of those...

                I have always used last years gas w/o issue. Make sure it has no water or seperated alcohol/water mix in it. Gas does not go bad in 3 days or even 60 days. It used to last over the winter w/o any additives, since at that time (70, 80s) the additives (AKA snakeoils) had not been invented. it is amazing that since stabilizer was invented, suddenly our gas spoils like milk left on the counter in the summer....


                • #9
                  Re: Shelf life of premix gas 50:1 ??

                  I just siphoned out 10 gals of last seasons fuel. How do you tell if it is contaminated? We have extreme temperature changes here in Colorado, I understand that is the culprit for water condensation
                  1980 175 Merc on a Glastron HPV-175 Bass Boat


                  • #10
                    Re: Shelf life of premix gas 50:1 ??

                    Interesting, A marina owner friend of mine stated in a tech session at his shop that gas in an enclosed sealed container loses just 1 octane per month. Now understanding what little I do about the very harmful effects of the other junk. Most of my older motors, run just fine on older gas, why I had one motor, that had 3 year old gas, and had not been started for that time period. Started on the second pull , and ran without fail until the tank was dry. The engine in question was a 1946 Mercury KD4. I will agree in principal that the newer engines have MAJOR issues with older fuel, the older engine have almost none.

                    The quality of the fuel in the 30's, 40's and 50's was no where near the octane of today, therefore I feel the older ones can be safely run on older fuel.

                    I love rambling about this. this all being said, I am alot more aware of how much fuel I use in a season, so I only buy what I will use in my collection for a season.

                    I currently own motors ranging in age from a 1914 Evinrude 2.5 hp Rowboat motor to a 1955 Evinrude 25 hp Bigtwin Electric. In 10 years of collecting and repairing ans restoring these type motors, zero failures due to bad gas.

                    Oh and if you wish to remove water from your fuel, here is a neat trick..

                    Take a pair of your wife's OLD, now I stress OLD panty hose, spray it with scotch guard, spread the panty hose over the opening of a funnel, the scotch guard should not allow the water to pass but the fuel will

                    That is enough for me tonight, enjoy the old ones guys, so much better than the newer motors


                    • #11
                      Re: Shelf life of premix gas 50:1 ??



                      • #12
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                        Re: Shelf life of premix gas 50:1 ??

                        well, all that said, my current batch of engines run between 1976 merc 20hp 1978 merc 20 hp to 1983 johnyrudes 7,5 and 15hp.
                        just this weekend i happily used 4 month old gas from my johnboat in my pontoon with the merc 20hp and ran between idle and 5800rpm til all 6 gal gone... no issues.... the other tank in pontoon had 4 gal of 7-8 month old fuel and ran like new as well.
                        things dif about my situation over others here i think.... I live in Arizona... Yuma to be exact and it is dry dry dry here.... never had phase separation in any fuel left for any time here, with one exception....... I also have an old gas can with leftover gas i use as parts wash....5 gal can...sits with vent open....the gas in it is currently 3 yrs old....with about 1 quart of newer fuel added from a recent jetski repair... it hasnt separated either...though it does smell "off" and i wouldnt use it in anything i wanted to keep by a long shot.
                        I personally think that the fuel going bad in 30 days or 90 days....or 6 months thing is bunk. that said, the one exception was fuel left in my quad for 2.5 years where it baked in sun, got cold, got rained that stuff... it separated... it changed color it smelled like turpentine.... heck it hardly wanted to burn when put on a parts tray and having a match flicked into it. I had the distinct pleasure of rebuilding and cleaning and degunking the mikuni carb on that one... and in the process found that old old old gas is rather abusive.
                        my parting thought is.... if i had a $15K engine or even a $5k engine likely after 30 to 60 days i would want new fuel to assure that the engine was getting decent fuel quality..... if i had 2 gal or 4 gal in a 25 gal tank... i would feel comfy just filling up and going... however if i had 20 gal....maybe time to transfer to my older and much cheaper engines fuel tanks. There is no harm done to an engine if you waste the old fuel and put fresh fuel in the tank.... but running old fuel in an engine you really care about could (not will) perhaps cause you some damage.... worth thinking about especially if you are not mechanically savvy. Do what your comfortable with... try not to buy more fuel than your going to use in a month and enjoy.

                        Let's Go Fishing!