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Old 07-19-2014, 08:41 PM   #1
wb22rules OP
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Stale Premix??

I am curious, whats the comfort range on shelf life on premix for you guys?
I usually will not use premix in any of my two strikes engines if it is more than 2-3 weeks old from a learning experience as a kid with my YZ and old premix that resulted in a top end job being needed.

I use ethanol free 93 octane that I have to drive 30 miles to get and runs almost 5 bucks a gallon, so re-purposing it for the lawn mower is not what I am fond of doing. I mix it with BelRay H1R at 80:1. Its not uncommon for me to mix a gallon, ride for an hour. and then not have time to ride again for a few weeks due to RL.
I am wondering if I can safely use the remaining half gallon after 3 weeks has passed or if needs to be converted into expensive lawn mower fuel used 1 part to 3 with regular gas.
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Old 07-19-2014, 09:15 PM   #2
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I run my premix 50:1 (vintage bike) with AVgas. I have let it set for months with no problems. I mix 2 gal. at a time.
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Old 07-20-2014, 05:28 AM   #3
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The oil acts as a stabilizer, keeping premix gas from going stale a lot longer than straight gas. I've used 6 month old gas and never had an issue in my trials bike. Not sure if I'd do that in a higher revving two stroke though.
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Old 07-20-2014, 05:37 AM   #4
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I use left over in something other than a 2t competition machine. It doesn't seem to gum up, but my bikes run better on fresh fuel. I've been told the oil mixed in breaks down and doesn't lube as well, no idea if that's true but I'd rather not chance it. The cost of fueling the bikes is so tiny it doesn't give me any pause to dump the left-over in the car or mower. BTW a mower will run just fine on an 80:1 mix :)
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Old 07-20-2014, 07:41 AM   #5
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I run race gas (AV gas in the boat) and no issues letting it sit for 6 months without additives. AV gas in the boat sat for 2 years and still wasn't stale.

A pressure washer will run nice and happy on 80:1 premix. That is about all I ever put in it. Just not worth keeping an extra gas can around with pump gas to go bad.
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Old 07-20-2014, 08:30 AM   #6
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If you store Race gas or Aviation Gas in a plastic container all the good things that make it a Better Gas will quickly pass through the plastic and leave you with crappy gas regardless if it is pre-mix or not. I will use premix for just a part of a season and use up the leftovers in my lawn mower and other gas power tools. Fresh is best!
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Old 07-20-2014, 07:48 PM   #7
wb22rules OP
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Thanks for the replies, I think I will keep being safe rather than sorry and continue re purposing premix older than 2-3 weeks to the lawnmower.
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Old 07-20-2014, 09:20 PM   #8
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Ryan Young told me my gas stunk last April at his trials school in NC. 60-1 Motul 2-T mixed with ethanol free 89 octane that was maybe two months old. Bike ran fine & never came close to fouling a plug.

While I miss the old days of Castrol, I think we're good here.
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Old 07-21-2014, 08:28 AM   #9
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There are legit concerns about storage time of fuels and oils, but as with anything that is complex, not so easy to directly see, and difficult to get hard scientific data on, opinions abound that sometimes can't stand up to scrutiny.

Colder, dryer, and more protected from sun and atmosphere leads to longer storage life. Every year for the last 40 years I have stored up to 9 vehicles and gasoline-engine-driven things containing E10 gasoline at a NM cabin. The most frequently-used vehicle will sit for at least 9 months, no problem, and some chain saws and other things have sat as long as 3 years with no problems. I have never spent money on a fuel stabilizer. Then again, it's high, cool, and dry.

Fuel and fuel-oil mixes in sealed containers kept in a protected area will last a long time. How long? That depends on the conditions of course, but talk of weeks? Unless fuel is highly contaminated, nah.

Chemicals can migrate through plastic, but but not so quickly in gas tanks and fuel containers. Cars and trucks have long had plastic gas tanks without a large number of mystery fuel failures in use or even after storage. If fuel is contaminated to begin with, or there is too little fuel in the tank (read on), maybe there will be problems after long storage.

An important factor in fuel life is its surface area time exposure to atmospheric or in- container gasses relative to the fuel volume. Sealed fuel tanks with more fuel in them: very stable. Fuel injected vehicles are very sealed. Carbureted things? Float bowls with a high surface area and very little fuel: not very stable! Float bowls have one or two float bowl vents, so a direct interaction with the atmosphere. That's why the fuel goes stinky and makes the vehicle a bitch to start later. Don't store float-bowl-based devices with fuel not run out or drained out. Chainsaws, for example don't have float bowls, and they keep longer.

You are better off storing with more fuel than less. No fuel at all is better than very little, but no fuel at all can lead to rubber and gasket bits drying out, shrimking, or cracking.

About ethanol, it's a favorite boogieman. Ethanol is hydrophilic. It loves to bind with water. Thus fuel additives long contained much alcohol to clean out water in fuel systems (before ethanol gasoline or if you refuse to use it). I don't prefer any ethanol to straight gasoline, especially above 10%, but if E10 is all that is available, I don't go driving around in a panic attack to find Billy Bob's c-store with the big "No Ethonal" banner. I use it and don't worry. I store it properly and don't worry. The thing to worry about with ethanol is when there is more water than can be bound up with. This is called saturation. With 10% of the fuel being ethanol, that's not much water. Here is a technical paper on that:

http://epa.gov/otaq/regs/fuels/rfg/waterphs.pdf

Have I had problems with ethanol gasoline? Oh yeah! I left a generator out in the rain once then put it up for 3 months. Somehow water wicked in through the gas cap into the half-full tank and the fuel evolved into an awful mess of cheesy substances. Had to disassemble and clean every bit of the fuel system.

If you keep your fuel dry via sealed containers, mostly full, and run your float bowl dry before storage, and the storage is dry and not above 80 degrees (the cooler the better - or just sgorten storage a bit if hotter), fuels will last a long time. It's mostly the screw ups that give E10 a bad rap, and once people turn sour on a issue, blame for lots of unrelated issues can get piled on. I don't like ethanol blends because blending was done more for political than technical or practical reasons. It's silly when it takes a lot of fossil fuel to produce a renewable.

motobene screwed with this post 07-21-2014 at 01:46 PM
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Old 07-21-2014, 11:44 AM   #10
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And if it smells like bad fuel, it's bad fuel.
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Old 07-23-2014, 09:04 PM   #11
wb22rules OP
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I used 2 month old premix when I was in HS on my YZ and totally flattened the top end. It probably has to do with the high humidity around here during summer months. In a cool dry climate I could see the fuel age issue being a non factor, but here in Central VA during summer months with 90% + humidity I think it can be a concern.
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Old 07-24-2014, 07:51 AM   #12
motobene
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Quote:
Originally Posted by wb22rules View Post
I used 2 month old premix when I was in HS on my YZ and totally flattened the top end. It probably has to do with the high humidity around here during summer months. In a cool dry climate I could see the fuel age issue being a non factor, but here in Central VA during summer months with 90% + humidity I think it can be a concern.
Sounds like an unsealed container problem? But what exactly does "totally flattened the top end" mean. Your cylinder and head squashed down to 1mm high?
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Old 07-24-2014, 05:06 PM   #13
wb22rules OP
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Quote:
Originally Posted by motobene View Post
Sounds like an unsealed container problem? But what exactly does "totally flattened the top end" mean. Your cylinder and head squashed down to 1mm high?

LOL, no not squished

I had been gone off of the farm for 2 1/2 months one summer, I came home and could not get a ride to the store to get some gas. I had some premix left I had mixed before I went away that summer and wasn't sure if it was good or not, but didn't have another option other than siphoning some out of a truck that would likely get gas in my mouth, and could possibly have gotten my tail whupped. I used the old premix to fill the tank twice that day. Took off and the bike was like a normal YZ 125D, powerband came on hard at 9k and would lift the front wheel easily in any of the first 4 gears. By the end of the two tanks of that old fuel I ran through it that day I could not get the powerband coming on to lift the front wheel in second. There was no big increase in power at that rpm any more. Granted the top end was two years old and needed to be refreshed, but the difference between the bike before those two tanks of fuel and after was very noteworthy. Ever since if it is more than 2-3 weeks old I try avoid using it in a two stroke I care about, like my bike or my chain saw. Weedeater, bleh who cares, but not the motors I like having snappy power.
I can't remember if the container that gas was in was had an opening, but knowing what was around in the 70s it probably did, and with the humidity here in central VA in the summer, that probably played a huge factor.

I got the cylinder bored 5 thousands, got a new piston and rings and man what a difference, it was pulling the front wheel up in 5th when it hit the powerband then.

Good times
Man I used to go through rear fenders back then.
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Old 07-25-2014, 07:26 AM   #14
motobene
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Originally Posted by wb22rules View Post
LOL, no not squished

I had been gone off of the farm for 2 1/2 months one summer, I came home and could not get a ride to the store to get some gas. I had some premix left I had mixed before I went away that summer and wasn't sure if it was good or not, but didn't have another option other than siphoning some out of a truck that would likely get gas in my mouth, and could possibly have gotten my tail whupped. I used the old premix to fill the tank twice that day. Took off and the bike was like a normal YZ 125D, powerband came on hard at 9k and would lift the front wheel easily in any of the first 4 gears. By the end of the two tanks of that old fuel I ran through it that day I could not get the powerband coming on to lift the front wheel in second. There was no big increase in power at that rpm any more. Granted the top end was two years old and needed to be refreshed, but the difference between the bike before those two tanks of fuel and after was very noteworthy. Ever since if it is more than 2-3 weeks old I try avoid using it in a two stroke I care about, like my bike or my chain saw. Weedeater, bleh who cares, but not the motors I like having snappy power.
I can't remember if the container that gas was in was had an opening, but knowing what was around in the 70s it probably did, and with the humidity here in central VA in the summer, that probably played a huge factor.

I got the cylinder bored 5 thousands, got a new piston and rings and man what a difference, it was pulling the front wheel up in 5th when it hit the powerband then.

Good times
Man I used to go through rear fenders back then.
Aha. That sound like an odd failure and I still have a hard time thinking it was from the fuel alone. If your tank was low and you put bad fuel in, you should have noticed the difference pretty quickly. It ran well at first, and that was with some pretty stale fuel in the float bowl.

You may simply have seized the top end for reasons other than, or just partially due to, whatever state the fuel was in. You may have finally worn out the mouse that was clinging to the air filter cage for deal life as you wheelied in 4 gears, finally sucking him in
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