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773 Posts
Not long enough...

Hopefully somebody with more knowledge on this subject will come along but in the meantime I know at least a little bit.

My father-in-law retired from a 20 something year career in an oil refinery and worked in avaition fuels for the airforce for a career before that. The very thing that allows for unleaded gas to resist moisture and stay fresh for at least the short term is the very thing (the additives) that go all gummy after six months to a year.

You can buy Stabil (guessing on the spelling) at Wallyworld for fairly inexpensive. According to the directions, the ounce or maybe two that you add per gallon will allow it to store for a year. They recommend doubling the amount for two years.

I haven't experienced anything beyond a year so I don't know but I have used gas at the one year mark with Stabil added and it seemed to work fine.

Diesel lasts much longer from what I've read but I don't know how much longer. The more refined the petroleum product is, the shorter it's lifespan. Unleaded gas is more refined from what I understand. Correct me if I am wrong anybody.

I asked Don (my father-in-law) about things such as Coleman's camping fuel or kerosene. He said anything without fumes lasts a good long while. I had a gallon of Coleman's fuel in my shop when I bought our house and the can was so old I had to use a pipe wrench to open the rusty lid. He took a whiff and said it wouldn't be a problem.

I try to keep at least 30 gallons of unleaded in plastic gas cans as well as the seven or so gallons my generator holds. I buy a fresh batch every winter because we have power outages from falling trees (Washington State, west part). I end up putting it through our vehicles after winter and keep a smaller amount on hand which ends up going through the weedeater and lawnmower over the summer.

I plan to make labels for my cans so I can write purchase dates down and we plan to up the quantity in storage but, if possible want to use it up within six months. If we go into a new dark age, heaven forbid, we will only have a matter of months to adapt to life without gas. In the meantime at least I can run our vacuum packer as much as possible as well as our propane camping stove for our pressure canner so we can can up and smoke and vacuum all of our meat in the freezer before the gas runs out.

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4,518 Posts
well i had 3 year old gas in a can I had to shake it to make it work better but it didnt run very well.. so I added new gas and it was fine.. you have to add something to the tank if you want to keep it longer..

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78 Posts
My old roomate had sunoco 94 sitting in the tank of his prelude for 14month's while the car and engine were being built. With around 11.5 to one compression after the build the old crappy gas still did ok. The car had a knock sensor but the gas had for sure lost some octane. If I were planning on storing gas for long periods Id get the highest octane you can get at the pump. 91-94

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1,349 Posts
the oldest gas ive used was three years old that somehow was forgotten in the back of a garage. it had 'sta-bil' added to it and the color was slightly off but smelled decent. the vehicle i added it to ran with no obvious problems.

i stockpile quite a bit of gasoline that is stabilized with 'sta-bil' and rotate it every year or two. ive never had any problems using gasoline that was up to two years old, which i do quite frequently. ive disassembled carb'd vehicles that ive used old fuel in and they look the same as the carbs in vehicles i didnt used old fuel in.

ive left cars, trucks, bikes, etc sit for years with unstabilized gasoline. the stale gas does horrible things to the fuel of which is leave some sort of funky rust-looking (although it isnt rust) gooey deposit on virtually every surface it touches. this glop clogs up filters, carbs, and fuel injectors as well as ruins fuel tanks. old stale gas has a peculiar smell to it that i cant quite describe but it doesnt smell like normal usable gasoline. almost like paint. stale gas tends to be more of an orange-ish brown color and not as clear.

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444 Posts
You seem to be more interested in gasoline so I will give that information first. One of the easiest solutions for questions concerning fuel storage like many others have said is a fuel stabilizer. PRI Advanced Fuel Treatments products for gas and diesel claim to have independent testing supporting an extension of useful life of both fuels for years and in many instances for 10 years or more with annual reapplication.

Chevron has also posted some storage recommendations concerning Longer-Term Storage of Gasoline at this link.

For long-term storage of gasoline, you might want to look into racing fuels. Some racing fuels (avoid oxygenated) have close to unlimited shelf life if stored properly. Check out

Anyway, here is some more detailed information concerning your question from British Petroleum.

Volatile fuels such as petrol and two stroke mixes will store for up to one year in a sealed container. After that period the fuel may still be fit for purpose but problems such as hard starting and spark plug fouling may occur due to lack of light components.

Once the seal is broken then lighter components evaporate and the storage life is best assumed to be 6 months at ambient temperatures of 20 deg C and 3 months at ambient temperatures of 30 degrees C or more.


Property_____________Week 1___Week 2___Week 3___Week 4___Week 5
% volume lost______________3________5________8_______10_______15
Octane RON_____________98.1_____98.4______98.6_______99_____99.5
Density kg/l 15 deg C_____0.75_____0.76_____0.765______0.78_____0.79
Equivalent air fuel ratio
at constant volume_______13:1___12.8:1____12.7:1____12.5:1___12.3 :1

At the end of 5 weeks the fuel is 5% heavier and the fuel air mix will contain more fuel.

Under normal storage conditions diesel fuel can be expected to stay in a useable condition for:
• 12 months or longer at an ambient of 20ºC (68ºF).
• 6-12 months at an ambient temperature higher than 30ºC (86ºF).

As diesel gets older a fine sediment and gum forms in the diesel brought about by the reaction of diesel components with oxygen from the air. The fine sediment and gum will block fuel filters, leading to fuel starvation and the engine stopping. Frequent filter changes are then required to keep the engine going. The gums and sediments do not burn in the engine very well and can lead to carbon and soot deposits on injectors and other combustion surfaces.

The expected life of a diesel fuel is indicated by the oxidation stability test ASTM D2274. The test measures how much gum and sediment will be deposited after keeping the fuel at 95°C in the presence of oxygen for 16 hours. It roughly corresponds to one year storage at 25°C. A result of less than 20mg/L of sediment and gum after the test is considered acceptable for normal diesel.

The ageing process can be accelerated by the following conditions:-
Contact with zinc, copper or metal alloys containing them. These metals will quickly react with diesel fuel to form unstable compounds.

The presence of water. Water allows the growth of fungus and bacteria, these produce natural by-products such as organic acids which make the fuel unstable.

Exposure to high temperatures.

Exposure to dust and dirt which contain trace elements that can destabilise the fuel, such as copper and zinc.

Fuel composition. Some components in diesel fuel naturally age quickly.

Prolonging the storage life is achieved by removing or controlling the conditions described in the previous section. Important measures to take are as follows:

Ensure that the fuel is not in contact with any surfaces containing zinc or copper or compounds containing those metals (e.g. brass). If those metals are present then a metal deactivator additive may help.

Establish a regular fuel maintenance program to ensure that water and dirt is removed from storage tanks. This will also remove any chance for fungus to grow.

Water should be drained from the storage tanks weekly. The frequency can be extended if the tank shows no tendency to collect water but should be done at least monthly.

Tanks should be kept full to reduce the space for water to condense, maintaining tanks half full increases the water build up and promotes corrosion in the top half of the tank. Most water will come from condensation as the tank breathes, the rate at which water collects will depend on local climate and will be higher in hot humid coastal areas.

Tanks should have a well defined low point where water will collect and can be drained. For example, cone down bottoms.

Establish a system for filtering the contents of the main storage tank through a recirculating filter system. This can be made automatic and will reduce the potential for problems by removing sediment and gums. The filters should be checked and changed at regular intervals. When the filter change interval reaches a certain frequency then the fuel should be changed over.

Tanks should be emptied and cleaned at least once every 10 years, or more frequently if there is a major contamination.

Ensure that the fuel supplied conforms to a recognised specification, in Australia that would be AS3570, and ensure the fuel matches the winter cloud point for the area to avoid filter blocking by wax drop out in cold weather. .

Always purchase fuel to replenish stocks in the winter season April - August. This will ensure that the fuel will not cause wax problems whatever season it is used.

Obtain assurances from the supplier that all components are fully refined to promote stability.

Establish a monitoring program whereby samples are taken at regular intervals to monitor the condition of the fuel. The samples can be examined at the site visually for evidence of haziness, sediment, darkening or sent to a laboratory for testing.

Regularly turn the fuel over. If possible, plan the fuel usage so that it will all be used within 1-5 years and replaced with fresh fuel.

The following additives can improve fuel storage life:
Metal deactivators. These work by stopping copper, zinc and other reactive metals from reacting with the fuel.

Fungicides/Biocides. These work by stopping fungus and bacteria from growing in the fuel and so prolong the life of the fuel. They are only effective on fungus and bacteria and will not stop other oxidation reactions from taking place. They are normally active at the water fuel interface where the fungus and bacteria grow. If fungus is present then a kill dose is required. Otherwise a maintenance dose is used to stop fungus growing. The disadvantages of biocides are:
• handling and mixing is hazardous because they are poisons.
• for a kill dose, killing the fungus can lead to a build up of dead matter which will block filters and also cause the fuel to oxidise.
• ideally, the fungus should be killed and then the tank emptied and drained out.
• maintenance doses are effective but no more so than regular water draining.
• disposal of water bottoms requires special handling with due regard to the environment.

Anti-Oxidants. These work by stopping the oxidation processes from taking place. They prevent the fuel oxidising and reduce the formation of sediment and gum.

Fuel Stability Foam. Fuel Kleenik is a stability foam which is suspended in the diesel fuel in the tank. It has been developed and tested by Department of Defence and is claimed to keep the fuel stable for up to 10 years. The disadvantages are:
• it does not work where fungus and water are present which is why it is suspended in the fuel.
• its size is 2100mm x 200mm x 200mm so it has to be dropped in through a hatch.

After 15 years it has to be disposed of to landfill.
Fuel Kleenik is available from a company called FuelTreat ph 1800 034 442.
In underground storage low sulphur diesel fuel can be expected to last at least 5 years provided steps are taken to keep water and fungus out and potentially up to 10 years or more with regular inspection.

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4,883 Posts
Stable temperatures, well sealed cans, and storage additives gasoline can be good for 1.5-2 years. I put my gas cans under a covered area and partially bury the cans in the ground. Roughly 1/2 in the soil. It helps stable the temps in the summer.

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5,854 Posts
FWIW... the half a tank of gas sat in mt 95 T-Bird for 14-15 months and when I replaced the battery and turned the ignition, it fired right up and ran like a champ. Passed a smog check too! That was pretty suprising as I was sure after that length of time I would have to drain and flush the tank. I drove 200 miles on that laft over gas in an effort to burn it up so I could fill it with fresh gas. I am sure this is the exception and not the rule though.
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