Modern gasoline shelf life?

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Modern gasoline shelf life?

Post by crypto » Mon Mar 12, 2012 12:54 am

I was looking at another thread discussing storing gasoline, and a few people are asking questions that I've never seen answered to my satisfaction.


Can you store modern (ethanol-blended) gasoline for any length of time without it pulling in moisture from the air and separating?

What are the best-case / worst-case storage times before the gasoline will dick up a modern fuel-injected automobile?

Are there any chemical stabilizers that will keep this from happening?

Is there anything creative one could do prior to sealing a storage container to prevent this from happening, such as shooting dry inert gas into the tank to displace the moisture-laden air?
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Re: Modern gasoline shelf life?

Post by JesterODX » Mon Mar 12, 2012 6:31 am

Good thread. Some questions I'd like to know as well.
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Modern gasoline shelf life?

Post by anonymac » Mon Mar 12, 2012 7:36 am

Most fuel stabilizer brands suggest 1-2 years storage life on gasoline, including blended fuels such as E85, and 2-5 years storage life on diesel fuel. Myself, I have actually used 2-year old diesel in my truck, and 16 month old gas in my mowers, both fuels were treated with Sta-Bil. No problems burning either of those fuels. Sta-Bil seems to do its job for me....

Alcohol blends tend to store longer on their own (without stabilizer treatment) than regular gasoline. This means they last in the can...We all know the horrors of leaving alcohol fuel in carbs and fuel lines....Just don't do it!
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Re: Modern gasoline shelf life?

Post by crypto » Mon Mar 12, 2012 10:14 am

anonymac wrote:Most fuel stabilizer brands suggest 1-2 years storage life on gasoline, including blended fuels such as E85, and 2-5 years storage life on diesel fuel. Myself, I have actually used 2-year old diesel in my truck, and 16 month old gas in my mowers, both fuels were treated with Sta-Bil. No problems burning either of those fuels. Sta-Bil seems to do its job for me....

Alcohol blends tend to store longer on their own (without stabilizer treatment) than regular gasoline. This means they last in the can...We all know the horrors of leaving alcohol fuel in carbs and fuel lines....Just don't do it!
With all due respect, a mower or other small engine isnt really representative of my question, which was regarding how it will fare in a modern computer-controlled ignition.

I've heard from multiple second-hand sources within the fuel industry that ethanol blends dont store as well as straight gasoline, I think that yours is the first input Ive ever heard to the contrary.
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Re: Modern gasoline shelf life?

Post by anonymac » Mon Mar 12, 2012 10:55 am

Here is a good (but long) white paper on gasoline and ethanol blends... http://ethanolrfa.3cdn.net/dd9e74ce1c45 ... 6bdgh3.pdf" onclick="window.open(this.href);return false;

There is quite a it of reading regarding performance of degraded fuels. The short version is that storage results in oxidation of fuel, which leads to reduced volatility and greater engine deposits. It should be understood that volatility is basically a measure of vapor pressure. Vapor pressure is how intensely a liquid attempts to turn to a vapor. We've all seen the fumes escaping from a gas can, and we've all seen a gas can swell while sealed and release that pressure when opened...Thats vapor pressure at work. As gasoline degrades (oxidizes), it loses that volatility (pressure). It still contains elements which burn readily, but they don't burn as intensely. This results in lower cylinder temps and lower cylinder pressures, which equal poor engine performance.

In the case of ethanol blends, specifically E85 or higher, the presence of ethanol reduces the volatility (vapor pressure) of the gasoline blend. This lower pressure equates to a slower oxidation process, which somewhat extends the storage life of blended fuel. Now this difference isn't great, so the shelf life won't be doubled or indefinite. It simply means E85 doesn't oxidize as rapidly as regular gasoline. This is why E85 vehicles have reduced power outputs. E85 just isn't as volatile. E85 will, however, absorb moisture more readily than straight gasoline. Again though, according to the white paper, the difference between the 2 fuels is somewhat minimal.

The biggest deterrent to storing ethanol blends is the effects ethanol and other additives on storage containers. The information Ive found on this is mostly directed at distributors and gas stations. Reading here: http://www.ethanol.org/index.php?id=55&parentid=29" onclick="window.open(this.href);return false; Basically, storing ethanol fuels in containers which are susceptible to corrosion is a bad idea. That includes fuel lines, carbs, etc...

I really think the white paper that I linked is probably full of the info you're looking for...Directly from the white paper:
Storage Considerations: Ethanol attracts moisture. If excessive moisture is absorbed, the ethanol and water can phase separate (fall out of suspension) from the gasoline blend. This would result in a mixture of ethanol and water in the bottom of the fuel tank. Aside from the fact that the engine would not operate on this ethanol/water blend, it can also
cause corrosion of various metals with which it comes in contact. However the potential for phase separation must be put in perspective. It would take almost four teaspoons of water per gallon to phase separate a gasoline ethanol blend. This would be an incredibly large amount of water to be accidentally introduced into the system. To absorb this much moisture from the atmosphere (at a relative humidity of 70%) would take hundreds of days even if the gasoline cap was left off. These concerns can be addressed simply by exercising caution that no water is introduced into the system. These precautions include a gasoline tank cap that seals properly and filling the tank before extended storage periods (note that some manufacturers recommend draining of the fuel tank and system before storage).
All gasoline, whether conventional, oxygenated, or re- formulated, deteriorates in storage. The gasoline "oxidizes" making it more prone to deposit formation. Because power equipment and recreational products are stored for extended periods, often six months or longer, manufacturers often make recommendations about storage.
A few recommend draining the fuel tank and fuel sys- tem. Many recommend treating the fuel with a fuel stabilizer which inhibits oxidation (i.e. anti-oxidant). Such products are available over the counter with one frequently recommended brand being STA-BIL. Some companies, including Briggs & Stratton, Toro/Lawnboy, and Yamaha sell a fuel stabilizer under their own brand name.
It is critically important that each manufacturer's storage recommendations be followed to the letter since gasoline is not usually of suitable stability for storage periods in excess of three or four months.
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Re: Modern gasoline shelf life?

Post by raptor » Mon Mar 12, 2012 11:51 am

anonymac wrote:Here is a good (but long) white paper on gasoline and ethanol blends... http://ethanolrfa.3cdn.net/dd9e74ce1c45 ... 6bdgh3.pdf" onclick="window.open(this.href);return false;

Great link! Thank you for the information.

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Re: Modern gasoline shelf life?

Post by KnightoftheRoc » Mon Mar 12, 2012 1:30 pm

Ethanol is also a water absorbent (hygroscopic) liquid. Combined with gasoline and water, it acts as a bonding agent between the two to create a single liquid which is still usable as a fuel, instead of separated into layers. It can also pull water from out of the air, and lock it into your fuel. I have never had much luck with gasoline stored for over a year, myself.

I do know that Sta-Bil is a reliable fuel stabilizer, keeping gasoline fresh for over 6 months at a time, if applied in the right proportions.
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Re: Modern gasoline shelf life?

Post by nes999 » Mon Mar 12, 2012 3:29 pm

I have used 1.5 year old gas in a truck. Granted i used sta-bil though

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Re: Modern gasoline shelf life?

Post by raptor » Mon Mar 12, 2012 4:01 pm

This is a big topic for discussion in boating circles. While many boats are diesel powered an increasingly large number use triple and quad outboards. They burn and store a lot of gasoline. The ethanol in some gasoline has played havoc with fiberglass tanks and the humid environment means that there is always water in the fuel...always.

This problem is a bit different. I suggest that stabil (or similar) be used and if at all possible increase the number of inventory turns (i.e. rotate the inventory more frequently). It is a PITA but that is one way to cope with the problem.

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Re: Modern gasoline shelf life?

Post by crypto » Mon Mar 12, 2012 4:03 pm

raptor wrote:This is a big topic for discussion in boating circles. While many boats are diesel powered an increasingly large number use triple and quad outboards. They burn and store a lot of gasoline. The ethanol in some gasoline has played havoc with fiberglass tanks and the humid environment means that there is always water in the fuel...always.

This problem is a bit different. I suggest that stabil (or similar) be used and if at all possible increase the number of inventory turns (i.e. rotate the inventory more frequently). It is a PITA but that is one way to cope with the problem.
Raptor, has anyone in the marine community looked at using CO2 or nitrogen purging in gasoline tanks to keep the atmospheric water out?
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Re: Modern gasoline shelf life?

Post by raptor » Mon Mar 12, 2012 4:13 pm

crypto wrote:
raptor wrote:This is a big topic for discussion in boating circles. While many boats are diesel powered an increasingly large number use triple and quad outboards. They burn and store a lot of gasoline. The ethanol in some gasoline has played havoc with fiberglass tanks and the humid environment means that there is always water in the fuel...always.

This problem is a bit different. I suggest that stabil (or similar) be used and if at all possible increase the number of inventory turns (i.e. rotate the inventory more frequently). It is a PITA but that is one way to cope with the problem.
Raptor, has anyone in the marine community looked at using CO2 or nitrogen purging in gasoline tanks to keep the atmospheric water out?
Not that I am aware of. What they do is top off the tanks and shut off the fuel tank vents to reduce the amount of moisture the fuel absorbs. However I doubt that does any good since when the boats are running the vents have to be open and the tanks get a load of hot moist air inside are the fuel is used. They take on fuel from underground tanks (generally) and as the fuel is put into the tanks, the cool fuel makes the moisture precipitate out into the fuel. SO I am not sure it does any good

The good news is that gasoline engines are more tolerant of moisture than diesel engines.


Here is a link to some of the fuel tank issues so if you have a fiberglass fuel tank beware:
http://www.boatus.com/seaworthy/fueltest.asp" onclick="window.open(this.href);return false;
Last edited by raptor on Mon Mar 12, 2012 4:43 pm, edited 2 times in total.

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Modern gasoline shelf life?

Post by hkusp1 » Mon Mar 12, 2012 4:19 pm

The tank I have in my mustang is a year old and it doesn't hesitate to start.

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Re: Modern gasoline shelf life?

Post by KnightoftheRoc » Mon Mar 12, 2012 4:22 pm

crypto wrote:
raptor wrote:This is a big topic for discussion in boating circles. While many boats are diesel powered an increasingly large number use triple and quad outboards. They burn and store a lot of gasoline. The ethanol in some gasoline has played havoc with fiberglass tanks and the humid environment means that there is always water in the fuel...always.

This problem is a bit different. I suggest that stabil (or similar) be used and if at all possible increase the number of inventory turns (i.e. rotate the inventory more frequently). It is a PITA but that is one way to cope with the problem.
Raptor, has anyone in the marine community looked at using CO2 or nitrogen purging in gasoline tanks to keep the atmospheric water out?
Not Raptor, but- this is a process that needs to be done at fueling time, and is pretty useless afterward. Gas tanks in older cars and trucks are designed to be vented to the atmosphere, and do this a few ways. Newer models use a sealed system, but it's designed to operate under a vacuum- adding pressure to it, required for this purging to work, would trip error codes in the ODB2 computer, and would screw you come inspection time.
Another downside to the system working under a vacuum (as fuel is drawn from the tank), is that the more volatile materials will vaporize first, to fill the space of the displaced liquid. Gas evaporates faster/easier than water, so the water content in the remaining fuel, even sealed off from outside air, actually increases slightly proportionally, as the space is filled with vapor.

For boating applications, it might work better- frankly, I don't know enough about those to say.
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Re: Modern gasoline shelf life?

Post by JesterODX » Tue Mar 13, 2012 6:42 am

hkusp1 wrote:The tank I have in my mustang is a year old and it doesn't hesitate to start.
It depends on the engine too. My grand mothers 89 Corsica set for three months and the gas gummed up the line and filter. My old 78 Scottsdale sat for two years, needed the top end rebuilt, but cranked right up after a new battery was tossed in it.

Some vehicles fuels systems are just better on the fuel. Sealed better or better material, IDK...
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Re: Modern gasoline shelf life?

Post by Mr.Pliskin » Tue Mar 13, 2012 12:42 pm

I know of gas that was siphoned out of a Kaiser ambulance that was probably 10 years old and put into a mercury montclair. While the fuel being burnt stunk and the car sputtered a lot it ran around for quite a while.

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Re: Modern gasoline shelf life?

Post by KnightoftheRoc » Wed Mar 14, 2012 7:42 pm

Mr.Pliskin wrote:I know of gas that was siphoned out of a Kaiser ambulance that was probably 10 years old and put into a mercury montclair. While the fuel being burnt stunk and the car sputtered a lot it ran around for quite a while.
This probably also (but not entirely) has to do with when the gas was made. I know I sound like an old fogey, but- the gas stored in our garage when I was a kid lasted longer than the additive-heavy stuff sold today.
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Re: Modern gasoline shelf life?

Post by DogLegArms » Wed Mar 14, 2012 10:54 pm

Does higher octane make a difference as far as shelf life?

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Re: Modern gasoline shelf life?

Post by raptor » Wed Mar 14, 2012 11:09 pm

Kimber 45 is a technician at the Chevron refinery in Pasgagoula, MS

Kimber_45 wrote:I do Octane testing on gas for Chevron. Here is a post from another site i did:

http://www.ar15.com/forums/topic.html?b ... 7&t=627380" onclick="window.open(this.href);return false;
Post from other site
Kimber_45 wrote: I was asked to post this, hoping I could give some info that may help someone. So here it goes, I work for a major oil company(Techron is our additive) and my job is to do all the octane testing on motor gasoline and aviation gasoline. I store gas at my home for emergencies and here are a few things to look for before storing gas.

1. Storing gas with 10% ETOH added will not store near as well as non-ETOH blended gas. Our refinery supplies a lot of gasoline to Florida, NE Alabama, Georgia, and up the east coast. The bulk of gas that goes to these areas is Sub-Grade octane gasoline. That means that it is made to an 84 octane and when it gets to the terminal, they blend it with 10% ETOH to raise the octane to 87( 91.5 base to get 93 with ETOH for premium). 10% ETOH gas will only store reliably for about 3 months, while our 87 octane with no Etoh is rated to store for 2 years without stabil or any other additive. We add an anti-oxident to the gasoline so it will not break down while in storage somewhere after it leaves the refinery. Not trying to ecourage it, but you can smell the ETOH in gas if you want to make sure you don't buy it for storage. The gas will have a sweet smell if it has ETOH in it.

2. You must be careful when adding large amounts of fuel stabilizers because they can lower the octane of your fuel. If your BOV is sensitive to the grade of fuel you use, either use a minimal amount or rotate your fuel more often.

3. Gasoline blended between Oct to April or so will have as much as 10-15% Butane added to it to help you car start in cold weather. If you bought your storage gas in this time, come summer when you need it, your car may have a rougher time starting since the Butane will have evaporated out depending on what type of storage container you are using.

4. Premium will store a little better than regular. The components used to make 93 octane are more stable and don't need as much anti-oxident in them. Refineries tend to throw a lot of products in regular just to get rid of them since that cant be made into anything else. You wont see this in premium.
Kimber_45 wrote:Here is some more info:

Gas without any additives should last for a minimum of 1 year. At our refinery, we put additives in to prevent gas from breaking down and to prevent corrosion. Some of the fuels that we use for certifications are 2 years old. Every 2 years we get new fuels so if stored right, it should last that long. (sealed 55gal drum).

Gas with ETOH added doesnt not store long because the ETOH will absorb water. ETOH can be removed from the gas be pouring water in the fuel. THe ETOH will become saturated with water and drop out of the gas. This is done as a field test. But once the ETOH drops out, your fuel is no longer a 87/91/93 octane.

In most instances, gas is gas, no mater what refinery makes it. All refiners have set standards from ASTM(American society of testing and methods) and API(American petroleum institute). What sets some apart is the additives in gas like our Techron.

As far as storage life from other refiners, I cant say. I know gas MADE at a Chevron refinery will store for 1 year without additives and I have used gas stored for 2 years at work. I wouldnt use gas stored for 2 years at home because 55gal drums of gas is a pain to work with if you dont have the right stuff like dollys and pumps.

Just because you fill up at a Chevron station doesnt mean it is gas MADE at Chevron, the gas could have been made at Exxon, Shell, BP, etc. They just put our additives in the gas.

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Re: Modern gasoline shelf life?

Post by 2now » Sat Mar 17, 2012 12:26 am

So who here has ever had gas go bad on them, with or without stabilizer?

untreated Gas can certainly gum up an engine, but I have kept untreated gas for 2 or more years, and ran the truck just fine when I put it in the tank. [ typically it goes in the tank of the moving truck before we pull out].

So who here has gas go bad on them in a can?
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Re: Modern gasoline shelf life?

Post by Killmoarzombies » Wed Mar 21, 2012 6:23 pm

I have first hand experience regarding this lol. I basically abandoned my crappy car at my work place for over a year. It had 1/4 tank in it and when I finally got around to starting it, the engine cranked right over. I'd say it's at least a year untreated :)

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Re: Modern gasoline shelf life?

Post by anonymac » Wed Mar 21, 2012 7:49 pm

Honestly, I think a person can rotate gasoline frequently enough there is no worry about it going bad. I keep 30 gallons on hand, and I can go through that in one summer mowing the yard. I also exercise the generator every 2-3 months. Occasionally dump a can into the car and refill the jug at the pump. Unless you're stockpiling hundreds of gallons, its easy enough to rotate and keep fresh.
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Re: Modern gasoline shelf life?

Post by Blacksheep » Sun Mar 25, 2012 4:40 am

So sealing it would not make it last a whole lot longer?

I heard from one source if sealed and under 7psi it will not seperate .... not sure If I buy it but The "7 psi" seemed rather specific for random bs lethal of truth perhaps ?
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Modern gasoline shelf life?

Post by anonymac » Sun Mar 25, 2012 7:20 am

Erie quiet wrote:So sealing it would not make it last a whole lot longer?

I heard from one source if sealed and under 7psi it will not seperate .... not sure If I buy it but The "7 psi" seemed rather specific for random bs lethal of truth perhaps ?

In regards to vapor pressure that I mentioned, 7psi would likely overcome the vapor pressure, but that would basically prevent evaporation. Need to look into that more though....
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Re: Modern gasoline shelf life?

Post by crypto » Sun Mar 25, 2012 7:53 am

Erie quiet wrote:So sealing it would not make it last a whole lot longer?

I heard from one source if sealed and under 7psi it will not seperate .... not sure If I buy it but The "7 psi" seemed rather specific for random bs lethal of truth perhaps ?
That would overcome the vapor pressure of the most volatile components in the gasoline, I'd think.
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