Petrol shelf life?

Its like asking how long is a piece of string.

Petrol evaporates over time, and it is this which means the tanks level drops, but as to how long it will stay fresh depends on many factors.
Petrol in an open or vented tank will begin to go stale as soon as it enters the tank, and its life is just a few weeks to be at its optimum. If additives are added they can prolong the life of the petrol, and many good additives are available, but generally expensive.

If the tanks are sealed, the situation inproves, this means the vapour is not escaping and the life of the petrol is longer.
 
This has been discussed many times on here. In the UK when I used to put my petrol boat away for the winter, I didn't drain the fuel tank in case the fuel went off before spring and it always started and ran fine on the "stale" fuel. So unless you are planning to leave your fuel hanging around for a couple of years, I wouldn't worry about it.
 
lovezoo said:
This has been discussed many times on here. In the UK when I used to put my petrol boat away for the winter, I didn't drain the fuel tank in case the fuel went off before spring and it always started and ran fine on the "stale" fuel. So unless you are planning to leave your fuel hanging around for a couple of years, I wouldn't worry about it.
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When I lay by bike up for the winter I always drain the tank to avoid condensation and water contaminating the fuel. Is this not a problem with boats?
 
Well, what I have done sometimes in the past is brim the tank so there is not much air in there to condense. At other times I haven't bothered and then topped the tank up with fresh petrol at the start of the season.

Both approaches have worked fine.

Bear in mind there is a water separating fuel filter on the engine, so any water that had come from condensation would be filtered out anyway.
 
lovezoo said:
Well, what I have done sometimes in the past is brim the tank so there is not much air in there to condense. At other times I haven't bothered and then topped the tank up with fresh petrol at the start of the season.

Both approaches have worked fine.

Bear in mind there is a water separating fuel filter on the engine, so any water that had come from condensation would be filtered out anyway.
Click to expand...

Thanks for the explanation, you learn something new every day on here. Well I do as I know vertually zilch about boats:)
 
I have heard unleaded loses something over time, but I have just used petrol that is at least a ear old, maybe more in an outboard. And it was fine.

However, perhaps in a high output machine, one would notice the difference.
 
I always store my unused outboard fuel (2 stroke) from one seasons to the next.

But

I always transfer it to tightly capped metal cans.

I only keep full cans ..
(any left over goes in the car or lawnmower)

The object being to prevent evaporation, limit contact with air and keep out of the light.

I always filter what has been stored before use and mix 50:50 with fresh.

(only once did I not filter it and that was probably the only time it would have been necessary :mad: )

Use of a fuel stabiliser might be advisable but I have not used one yet. Sta-Bil is very popular in the USA.

If/when we are all using a high ethanol fuel things may change and we may find storage times reduced considerably.
 
I was talking to a customer recently who races go carts, he said after a few weeks if not used he would change to fresh fuel. He said for better performance.
David
 
DIW said:
Is it true that Petrol has a limited shelf life and goes stale?
If so can anybody advise what the recommended maximum storage period is please.
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Thanks for the reply's all - the reason for the question is I keep a full 5 litre plastic fuel container for use with the aux. outboard which I only fire up before a trip and sincerely hope I never have to use in anger so I only use a very minimal amount of fuel from the container.
On reflection its probably more sensible to pour the container into the main tank periodically and then re-fill it.
 
Petorl does degrade over time, as the "lights" evaporate off. Your fuel tank should have a vent, otherwise as the bulk fuel temperature increases, then it can go pop.

In a relatively low performance engine in a boat, I did not really notice any difference in starting or performance after the winter, but as others have said, it will be noticeabe after a couple of seasons.
 
I had an old Fiat Cinquecento sitting in the garage for eight years. The tank was about 1/4 full.
On fitting a new battery, the electric fuel pump whirred away, and she started first turn of the key.
Beyond that, I know nowt!
 
When we bought our boat she had been sat on the hard for 3 years with 3/4 tanks.

Was a little concerned but was told it wouldn't do any harm so started them up, started no problem and ran absolutely fine on it, when the tanks were empty enough to top up with a meaningful amount I put 3/4 of a tank of new fuel in both sides.

There was no discernible difference at all, have since been told that carburated Volvo V6's will run on anything flammable so maybe it is different for other engines.
 
unleaded fuel tends to throw a precipitate of a jelly like substance which tends to block jets in carbs etc, and which sets to a clear varnish like layer. However once this has been done i have used "stale" fuel sveral years old without problem. If this was in a high compression engine then there may bea problem, but in marine use I DOUBT IT
 
My honda generator got started today with fule about 4 years old, i pulled the cord a few times to move the oil and turned it to start and it fired 2nd go. Petrol may go off a bit but it will always fire up. Same applys to the 'gunking' up of the carb, never cleaned the carb in any gennie i have owned and they all worked just dandy:D

Some on here can be a little extreme, same as those over on a well known car detailing site...OCD:D;)
 
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