Petrol shelf life?

[Mixagon_imp]

So we are told that petrol has a shelf life 3 to 6 months after which it starts to lose its octane the combustible part but can last up to 15 months with fuel stabilizer.
That's what I thought until recently when an elderly neighbour who stopped mowing her lawns herself 4 years ago offered me a can of petrol which was for her mower. She had meant to give it me years ago but kept forgetting.
I took the gift mainly for future use of the can but couldn't help wonder what state the nearly 5 year old petrol would be in.
I have 5 mowers so chose one I never use which had been stored for many years with an empty tank and filled it with the old fuel, primed it and first pull it started and is being used weekly on the old fuel with no loss of power at all.

Ok the petrol looks darker than usual and I wouldn't risk it in a vehicle but it just goes to show it can still be used after 4+ years with no stabilizer.

[the Ferret]

Wow amazing

[j3gq_imp]

Not sure this is a surprise. The donated fuel has - no doubt - started decomposing like any other fuel. But it was held in a sealed container ( unlike gas tanks in cars, m/c or airplanes or in carburetors ). So after the vapor pressure of the most volatile components had built up in the can, further loss of these components stopped.

Next, when you poured it into the tank of your mower #5 some if not all of the built-up residues stayed at the bottom of the can (I suppose you did not shake the can wildly before pouring ?). So the fuel - which worked seemingly fine in your mower - is different in two ways from bad fuel in a tank or in a carburator after 4 years. First it didn't lose all volatile components, second what fell to the bottom over the years remained in the can. In a carb it would have blocked the nozzles.

With your carb (probably) kept dry while not in use, the engine was ready, the carb was ready, and the fuel simply had less energy content (per kg or liter). Knocking would have occured with the gift fuel in larger cylinders sizes (diameter matters, not stroke) and at higher temps, but this cannot be seen in your lawn care machine.

[PowerDubs_imp]

Agreed- carbs hate sitting with old gas.

But old gas can run in a carb.

Fuel injected engines are MUCH more tolerant.

I personally know of cars that have sat for 5-6 years and start right up and run fine.

[pekingduck]

I presume the can was nearly full, and sealed tight, so there was a limited amount of air inside from which moisture was drawn.

[GoldOxide_imp]

... there is hope for gasoline during the Apocalypse.

[rich_imp]

does the fuel in the UK have ethanol ?

[Tev62]

does the fuel in the UK have ethanol ?

Yes, Ireland too, mainly 5% now but increasing to 10% shortly.

[j3gq_imp]

... there is hope for gasoline during the Apocalypse.

There is hope for many things, ... like for gas, for bacteria, for rocks, for slime, and - a recent study shows - for jellyfish of all. But there is little hope for anything mammalian. Our countdown is running, and all we have to do is to patiently wait for the last man and last woman on earth to agree that something needs to be done (it is sooo hard to act before then). Until then we play musical chairs and keep burning oil and coal.

[Mixagon_imp]

does the fuel in the UK have ethanol ?

Yes, Ireland too, mainly 5% now but increasing to 10% shortly.

Yes, Ireland too, mainly 5% now but increasing to 10% shortly.
We have had 10% for a while now
I always go for the premium fuel which has none supposedly but its dearer of course.

I presume the can was nearly full, and sealed tight, so there was a limited amount of air inside from which moisture was drawn.

That is so but I did transfer it to a another can straight away and there was nothing at the bottom.

I do wonder how old the petrol is at filling stations as it keeps being topped up new on old and the tanks are not airtight. We could be buying a mixture with some parts being 10 + years old before we get it.

Maybe the shelf life is a myth to try and stop people storing it?