How long is gas in a tank ok to use?

[DanceLvr]

Hey my kid brother has this 2007 Yamaha Waverunner thats been in storage out at our parents place sne since he joined the Navy in 2009 and now he says he wants to sell it. It's newer and has lower hours than mine so I was going to see if maybe I could sell mine and buy his and got his OK. Thing is it's not been started since early summer 2009. Now he says that he put in gas stabilizer and filled the tank as full as it would go with quality Shell gas. My dad looked at it the other day and said everything else seems OK but he's not sure about running it on two and a half year old gas.

How long is gas OK to use even if it has stabilizer stuff in it?

[jobrown]

If it runs that's fine, you will experience a decrease in power I would think... As gas ages it denatures, the molecules actually start to fall apart. It's the breaking of these large molecules that releases so much energy, so if the old gas already has a lot of broken molecules it wont have as many to break and therefore not as much energy to use!

But yes, if it runs, run it. Seafoam is always a good additive to get some older gas back some of it's punch. I've used it successfully.

[550rider]

Beeee careful... Sometimes gas sitting in carbs that long will cause rubber seals to fall apart... My personal opinion, I would tear the carbs apart see what I have, rebuild carbs,empty tank, a local jiffy lube will take gas I believe. start fresh, it's gonna run like crap anyways with that gas, it's not worth the money you save. I also know some small engine mechanics that swear old gas blows engines up... I couldn't tell you why. I hate running my engines on 6mo old gas let alone 2 years old, even will stabil.

[SouthernGypsy]

Re: How long is gas in a tank ok to use?

We own a restoration and custom automotive shop and very often deal with classics we buy to restore that have been sitting up and have very stale gas and we have learned a lot over the years in dealing with stale gas, usually much older than what your referring to.

OK, while there is a limit to the useful age of fuel your only talking a couple of years and gas of that age, especially with Marine Stabil or another quality stabilizer will still be good after that long. If he did indeed fill the tank as full as possible that's great as well. One of the major detriments to older gas that has been sitting is that it draws moisture but it's the air space in the container that it's in which determines how much moisture will be present, a full tank means less air space and less chance to draw moisture, that's why a tank should always be full when you store a watercraft for the winter, or any vehicle for any length of time. You should be able to put in one can of Seafoam and be fine running it, a Waverunner of that era will be direct fuel injected I think, at least my 2006 was so a 2007 would clearly be, though mine was an FX High-Output and that may make a difference if his is just a VX. You didn't mention and I'm not certain about VX models anyway in comparison to FX HO's.

If you pull it very far to get to the lake after putting in the Seafoam that will also help, the vibrations from pulling it helps mix the Seafoam throughout the fuel and helps "stir up" the fuel itself a bit, it helps re-airate the fuel as well. All fuel has O2 suspended in it on a near-molecular level and over time that also dissipates some which is part (though only one part) of why gas goes "stale", along with the partial separation of some of the base chemicals. The shaking/mixing is just like shaking any kind of container with liquid, it helps reintroduce air into the gas and also helps re-stir those chemicals a bit... NO, it will not be like fresh gas no matter how much you shake it... but it does help a little. If you do run it that way then as soon as you have a little space, say when it's down to 3/4 of a tank, add some fresh gas in. Fresh gas mixed with old gas does help the old gas to burn more successfully. The fresher gas helps sustain the combustion process more fully. That time run it down to 1/2 a tank and then refill it again. After that just run it like you normally would, by then you have enough of a fresh gas to old gas ratio that it's no longer a concern.


Now, that is one way. However, The ideal thing to do it would be if you have some gas cans and can siphon the gas out of that tank. If you can siphon out enough to get the Waverunner down to 1/4 or 1/3 of a tank or less that would be great, then just add the Seafoam and refill the rest with fresh gas. That much fresh gas mixed into only 1/4 to 1/3 of a tank of the older gas will run perfect at the age your talking and even older and you don't need to do anything else special. I have seen that trick done with gas as old as 10 years that didn't even have any form of stabilizer.

As for the gas you siphoned off into cans, you don't have to loose that either, Just take the cans and put them into your regular vehicle so long as it already has at least 1/2 of a tank of fresh gas. If you have a vehicle with a really small tank and you got a lot of gas out of the Waverunner then just put in 5 gallons at a time. There is a second reason this is the more ideal way of doing it... cars and trucks are more tolerant of running old gas than smaller engines such as in watercraft. The larger the engine the more tolerant it is, that is to say a V8 pickup engine will be more tolerant than a 4 cylinder engine in a small economy car. This method lets you get mostly fresh gas into the watercraft and at the same time not have to dispose of any gas, which at today's gas prices every gallon counts, and the old gas mixed in with a half of a tank of fresh gas in your vehicle will run perfectly in your vehicle as well.

[550rider]

This guy knows his sh1t! Disregard my comment! I think I'll try that method next time I run into old gas

[anthrobe]

Re: How long is gas in a tank ok to use?

Why take the risk? Siphon it out and replace with new. I will not run gas in my ski that is more than 2 months old.

[DanceLvr]

Re: How long is gas in a tank ok to use?

Thanks to everyone for their advice. We tried to take Southerngypsys advice but it turns out the waverunner has something in it that prevents siphoning the gas out. My father was trying to help me this weekend and he couldnt get even a small stiff hose through. But he had heard of that Seafoam stuff too and so we got a can of that and put in and then tried adding more fresh premium to it, it was full so only got 1.3 more gallons into it and that was filled right to the rim but we ran it that way until it was down to about 2/3 of a tank and topped it off again, then ran it down until it had 1/3 of a tank and topped it off again. played with it all weekend on tenkiller and never had a problem with it.

[SouthernGypsy]

Re: How long is gas in a tank ok to use?

There's no need for that though, gas that is only 2 months old even without any kind of stabilizer is still totally good. It doesn't even begin to go stale at all until closer to 6 months at the very minimum. A good stabilizer such as Marine Stabil will extend that upto a year.

Why take the risk? Siphon it out and replace with new. I will not run gas in my ski that is more than 2 months old.

[SouthernGypsy]

Re: How long is gas in a tank ok to use?

Glad it worked and sorry, I forgot to mention that you can't siphon from a Waverunner built after 2004 to help deter theft, but if you take the seat off and look at the top of the tank there is a rubber cap held on with a stainless hose clamp that you can take off and then insert a siphon hose directly down into that. Glad the other method worked out for you though, I was sure it would be ok, like I said, we've had a lot of experiance with vehicles that have sat up for long periods so it's nothing more than that experiance and trial and error over the years to learn what does and doesn't work and how long gas can still be safely used without risk in different types of engines.

Thanks to everyone for their advice. We tried to take Southerngypsys advice but it turns out the waverunner has something in it that prevents siphoning the gas out. My father was trying to help me this weekend and he couldnt get even a small stiff hose through. But he had heard of that Seafoam stuff too and so we got a can of that and put in and then tried adding more fresh premium to it, it was full so only got 1.3 more gallons into it and that was filled right to the rim but we ran it that way until it was down to about 2/3 of a tank and topped it off again, then ran it down until it had 1/3 of a tank and topped it off again. played with it all weekend on tenkiller and never had a problem with it.

[j0816]

Re: How long is gas in a tank ok to use?

I won't burn old gas in my ski from the last fall even though I stablize it,lets just say i'm stablizing it for the lawnmower or weed eater,its not worth it, gas that has lost it octane can cause your engine to predetonat: 10 gal. gas and premix 50.00, refurb shortblock 800.00 if you put it in yourself.

[SouthernGypsy]

Re: How long is gas in a tank ok to use?

Gas doesn't loose octane that fast though, I was a tactical driving and security specialist for years for the government and this is one of those facts they made us learn in class way back when and teach to new students today. The minimum standards in the US for what the industry refers to as storage stability rating says that in a sealed container with less than 5% vulume of air space present vs. volume of fuel and either air tight or with a proper sized vent for the container require that common pump gas must be able to last a minimum of 9 to 12 months with less than 1 point of octane loss and less than 1.2% degridation in overall formuation stability. That's at 9-12 months and even then you wouldn't get detonation with only 1 point of octane loss, not if your ski is tuned properly to begin with. If your getting detonation over that little of a drop then somethings wrong with the ski anyways. Most gas at the pumps can show almost 1 point of octane loss just brand to brand sometimes. Aside from the standards and what they thought us, a life of experiance restoring classic and collectable cars has only taught me from experiance that gas is actually more stable in storage than some people think. Most degredation from my experiance has more to do with the container (rust, scale, allows excess moisture in, etc) than it has to do with the gas itself degrading on it's own. The good news is that PWC's have plastic tanks and they don't rust, they don't scale, they don't let in too much moisture if you have the proper cap on and your vent lines are in good shape, and as long as you use good gas that's not contaminated in the first place (such as pouring out of another container that may have contaminents in it) then they generally store very well, especially if you keep them near-full.

[dorny119]

Re: How long is gas in a tank ok to use?

Old thread. But wow, SouthernGypsy seems like he knows his stuff. I have honestly never had any problems with fuel sitting in my tank for 5 months or so.