What’s up with this fuel?

[Grit dog]

So not about a Square, or even a vehicle.
The last year or so, this is the second time this has happened to my pre-mix 2 stroke gas.

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Yea that is pretty fresh 2 stroke mixed gas in the cup. It’s about 2 month old Av gas (blue) with Amsoil Interceptor oil (oil is natural or brown color) but also happened with Klotz oil (red color).
Gas can is a metal safety can in good condition, except I can’t see in it through the flash screen. Although it’s had only mixed gas in it for at least 10-15 years. Seal on the lid is good and it’s had oily gas in it exclusively. Can’t imagine it’s rusted. Have far older and or worse condition of the same cans plus the ones we use at work which are constantly subject to weather.

Same thing happened a couple tanks of gas ago. Just turned dark piss yellow/brown. Still smells right and Av gas is supposed to be stable for something like 2 years. The rest of the can of Av gas I mixed this from is still bright blue.

But it doesn’t burn right. Idles fine but bogs down. Made a new batch of premix again and the ole leaf blower ran right again immediately.
I’m stumped.
Made another gallon of premix in a plastic can to see if it’s the can or not.
Anyone with any experience with gas that goes bad this fast? Or why?

 

[Radiohead]

Condensation on the inside milking out the oil is the only thing that popped into my mind. Plastic is way less susceptible to it.
Is it's location temperature constant or like outdoors? Sun exposure is another thing. I'm going with internal condensation fouling your fuel for the win.

 

[fast 99]

1 oz Stabil to 2 1/2 gallons of e free. Have been using that mix for at least 10 years. Never had an issue.

AV gas by itself is very stable, 2 years at least, sealed. The formulation is a completely different animal compared to pump gas.

A friend used AV gas in a lawnmower and stuck a piston. I wouldn't use it in power equipment.

 

[Grit dog]

Condensation on the inside milking out the oil is the only thing that popped into my mind. Plastic is way less susceptible to it.
Is it's location temperature constant or like outdoors? Sun exposure is another thing. I'm going with internal condensation fouling your fuel for the win.

Noticed now I’m apparently repeating myself like an old guy since I posted this the last time it happened.
It’s not in a conditioned space but rather sits on the concrete floor in the shop in a temperate climate.
That’s a very plausible explanation though.
Happened earlier this year with fuel AV mixed up probably the previous year.
Had 1 more batch that apparently lasted from June until a month ago no issue, used it all up.
Now again same thing a month old.
This can I used new 2s oil.
Someone mentioned water or JetA contamination. Plausible. But the jug of pure gas is still blue as the sky. And what’s more, I’m sure some of the leftover gas from a previous jug is in my bike. Checked it. Been in the bike tank (no oil, 4s) since April. And it is still good.
I’m calling the metal can suspect for one reason or another.
Mixed up just a gallon this time in a brand new fangled stupid plastic gas can. With new oil and AV that is still blue and pretty fresh.
If it keeps well then I can blame the metal can I suppose.

Stupid thread I know. But you guys are the biggest group of very knowledgeable gear heads I know! So best place to ask.

 

[Shorty81]

Never used av gas, but I use Rec 90 (marina) in all my power equipment and my sawmill. Never had any issues. It's also ethanol free.

 

[Grit dog]

1 oz Stabil to 2 1/2 gallons of e free. Have been using that mix for at least 10 years. Never had an issue.

AV gas by itself is very stable, 2 years at least, sealed. The formulation is a completely different animal compared to pump gas.

A friend used AV gas in a lawnmower and stuck a piston. I wouldn't use it in power equipment.

Interesting on the stuck piston. I know 100LL is a no no in anything that lead would hurt. And have heard “stories” of lead buildup on valves and messing with efi.
I’ve been using 100LL for 2s mixed gas for over 5 years now. Started it only because no need to worry about bad gas and draining/running empty all the little 2smoke yard tools.
The stuck piston makes no sense. From a lubrication or heat standpoint in my limited experience. If anything it’s a loss of power from the slower/cooler burn. But I don’t discount your experience. Although it doesn’t compute with me.
As more evidence, I have a buddy who is admittedly one of the best mechanic, rider, racer, welder, autobody all around genius gear heads I know.

Yet he still believes that “everything” runs better on race gas and buys it by the barrel. Using it in many things not needed or intended. And his outcome doesn’t support that. (He doesn’t use C12 in the lawnmower, but runs stock bikes on it that are ridden hard).
I am interested in knowing why too much octane could contribute to detonation or high heat though as I’ve always thought the opposite.

 

[Grit dog]

Never used av gas, but I use Rec 90 (marina) in all my power equipment and my sawmill. Never had any issues. It's also ethanol free.

Totally. Idk if it’s still true but even less than 10 years ago, Rec90 was all you could by at any normal gas station in Alaska. For the stability.
If it happens again I’ll scratch the 100LL for my premix. But around here it’s costs about the same as ethanol free premium and by rights should have at least 3x the shelf life.

 

[fast 99]

Interesting on the stuck piston. I know 100LL is a no no in anything that lead would hurt. And have heard “stories” of lead buildup on valves and messing with efi.
I’ve been using 100LL for 2s mixed gas for over 5 years now. Started it only because no need to worry about bad gas and draining/running empty all the little 2smoke yard tools.
The stuck piston makes no sense. From a lubrication or heat standpoint in my limited experience. If anything it’s a loss of power from the slower/cooler burn. But I don’t discount your experience. Although it doesn’t compute with me.
As more evidence, I have a buddy who is admittedly one of the best mechanic, rider, racer, welder, autobody all around genius gear heads I know.

Yet he still believes that “everything” runs better on race gas and buys it by the barrel. Using it in many things not needed or intended. And his outcome doesn’t support that. (He doesn’t use C12 in the lawnmower, but runs stock bikes on it that are ridden hard).
I am interested in knowing why too much octane could contribute to detonation or high heat though as I’ve always thought the opposite.

It happened in a 4 cycle lawnmower on a very hot day. It's the only time I heard anything like that, but I am not taking any chances using it.

Like I said have been using Stabil and E free for years. Although probably not a good idea [with the exception of a 2 cycle snowblower] don't run any power equipment out of gas for storage either. Do have a heated shop.

I do have several old cars without hardened valve seats. One of the reasons lead was added to fuel. They always get a mix of av gas. If you have time, AV gas formulation and requirements are interesting. Search the internet. One thing however, the EPA is banning leaded aviation fuel. There are a couple alternatives none are approved yet, but it's coming.

 

[Grit dog]

@fast 99
Yeah we all have our own “donts”. Not doubting you.
I smoked a snomachine piston once (well more than once, lol) but this one was no reason other than I attribute it to using methanol HEET. Now I won’t use yellow bottle heet in 2 strokes. Haven’t needed to use any at all in 20 years so go figure …
I don’t need the lead, obviously, but it’s just too easy for all the small tools to not have to drain and run dry. Guess I traded stabil and seafoam for AV.

 

[fast 99]

@fast 99
Yeah we all have our own “donts”. Not doubting you.
I smoked a snomachine piston once (well more than once, lol) but this one was no reason other than I attribute it to using methanol HEET. Now I won’t use yellow bottle heet in 2 strokes. Haven’t needed to use any at all in 20 years so go figure …
I don’t need the lead, obviously, but it’s just too easy for all the small tools to not have to drain and run dry. Guess I traded stabil and seafoam for AV.

Yes, do whatever works. I laugh at people buying fuel antifreeze, they have no clue. AV gas smells good too.

 

[Grit dog]

Yes, do whatever works. I laugh at people buying fuel antifreeze, they have no clue. AV gas smells good too.

Nowadays it largely a non issue due to the ethanol content, for sure.
I used to religiously pack a bottle of Iso HEET in my snomachine tool kit for real reasons.
Now with better care than of my machines (which sometimes run corn whiskey laced fuel) and less water in fuel problems I’ve stopped doing that.
Also most of my riding is in the “warm” Cascades. If I was going into the backcountry in a cold climate I’d still pack some with me for sure.
But only snomachines. Haven’t even picked up a bottle of Yellow HEET in 25-30 years!

And yes AV gas, especially mixed with oil smells good. Makes you think you’re doing something fun with race gas when you’re actually doing yard chores!

 

[OldBlueDually]

I would agree with condensation in the metal can. You trying out plastic would be the way to go, I always use plastic gas cans and mix a ton of 2-stroke in the winter for my old snowmobiles.

What exactly are you using AV fuel for anyhow? I would suggest not using that, and stick with no higher than non-oxy 91 octane in all older 2-strokes (most newer 2-strokes & their plastic/rubber items can handle regular 87 to 90 octane) if you have it available as it also lasts longer, and does not harm plastics/rubbers like most ethanol's do. Use stabil if you are concerned about it sitting.

What @fast 99 stated about a stuck piston, is actually very accurate with any type of 100 AV (including 100LL), or higher octane fuel. Unless you have the compression to run it, don't. If your 2-stroke is at 12:1 you might be safe to run AV, but I doubt you have that kind of compression. 12:1 is a must for 110 octane.

What happens in a 2-stroke engine (although 99 mentioned 4-stroke, but the same happens) is the AV, or 110 fuel used in those does not fully burn, and it eventually washes the cylinders, then you toast your engines, and yes it can make a piston stick right to a cylinder.

It happens a lot with people thinking they can run 110 (around here at least) because it "performs so much better"....but it doesn't perform better in the least, they smell race fuel & think they are automatically performing better.....kinda like "loud pipes means it's super fast"...BS.

You mentioned "slower/cooler burn" and that is very true: In a 2-stroke you do NOT want that. You want a fast burn, right now. Hence the difference in spark plugs too in 2-strokes. NGK's B7 is a hotter running plug than a B8 on up (most plugs like champion, the higher the number the hotter--not NGK).

So even if you put in a warmer burning plug in your 2-stroke, and you run AV or 110 you are doing it harm. I would say you are luck you have ran whatever it is you have for this long.

As for mixing purposes, all my old sleds get 40:1, even though the new oils are far superior than the old oils and I could lean them further (back in late 60's & early 70's 24:1 was suggested), but I don't. With new stuff I have that takes premix, those are 50:1--Better to lose a spark plug than burn up an engine.

Sorry to go on a rant here, I hope you find something here useful.

 

[Bextreme04]

I would agree with condensation in the metal can. You trying out plastic would be the way to go, I always use plastic gas cans and mix a ton of 2-stroke in the winter for my old snowmobiles.

What exactly are you using AV fuel for anyhow? I would suggest not using that, and stick with no higher than non-oxy 91 octane in all older 2-strokes (most newer 2-strokes & their plastic/rubber items can handle regular 87 to 90 octane) if you have it available as it also lasts longer, and does not harm plastics/rubbers like most ethanol's do. Use stabil if you are concerned about it sitting.

What @fast 99 stated about a stuck piston, is actually very accurate with any type of 100 AV (including 100LL), or higher octane fuel. Unless you have the compression to run it, don't. If your 2-stroke is at 12:1 you might be safe to run AV, but I doubt you have that kind of compression. 12:1 is a must for 110 octane.

What happens in a 2-stroke engine (although 99 mentioned 4-stroke, but the same happens) is the AV, or 110 fuel used in those does not fully burn, and it eventually washes the cylinders, then you toast your engines, and yes it can make a piston stick right to a cylinder.

It happens a lot with people thinking they can run 110 (around here at least) because it "performs so much better"....but it doesn't perform better in the least, they smell race fuel & think they are automatically performing better.....kinda like "loud pipes means it's super fast"...BS.

You mentioned "slower/cooler burn" and that is very true: In a 2-stroke you do NOT want that. You want a fast burn, right now. Hence the difference in spark plugs too in 2-strokes. NGK's B7 is a hotter running plug than a B8 on up (most plugs like champion, the higher the number the hotter--not NGK).

So even if you put in a warmer burning plug in your 2-stroke, and you run AV or 110 you are doing it harm. I would say you are luck you have ran whatever it is you have for this long.

As for mixing purposes, all my old sleds get 40:1, even though the new oils are far superior than the old oils and I could lean them further (back in late 60's & early 70's 24:1 was suggested), but I don't. With new stuff I have that takes premix, those are 50:1--Better to lose a spark plug than burn up an engine.

Sorry to go on a rant here, I hope you find something here useful.

Most aircraft engines that spec 100LL are only running 8.5:1 compression or so. They have a large displacement and long stroke to take advantage of the slow burn and also two spark plugs per cylinder to help the mixture fully burn.

Like you said.. the slow burn in a single plug, short stroke, high revving engine is a recipe for disaster.

I'm a big fan of non-ethanol premium in all by small engines. It's also about $2/gal cheaper than 100LL around here.

 

[fast 99]

Engine Masters dynode various octanes. There was very little change in HP. Came to the conclusion excess octane is a waste of money.

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[Radiohead]

My BIL hates that episode. He hates how I flick him $#!t about this, but it's not my money being converted....