Can petrol go off

Bigplumbs said:
What are your real world experiences of this I wonder
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My real world experience is with a Mercury 5hp that refused to start and run on the previous season's fuel.
I took it in to a dealer, who ditched the fuel, put in fresh fuel, and it started on the second pull.
I think heat is also a factor ... the petrol can was stored in the cockpit where it got quite warm, and the more volatile components probably disappeared.
 
SC35 said:
My real world experience is with a Mercury 5hp that refused to start and run on the previous season's fuel.
I took it in to a dealer, who ditched the fuel, put in fresh fuel, and it started on the second pull.
I think heat is also a factor ... the petrol can was stored in the cockpit where it got quite warm, and the more volatile components probably disappeared.
Click to expand...
well there you go ,, my 5 h Yamaha sat for almost a year and started first pull ,, we almost could not believe it (y) ( i dont know how well or for how long it would have ran as we turned it off again immed )
 
bru speaks the truth.

fuel does go off over time, whether it goes off enough for you to notice it through a rough running or even none starting engine depends on the engine.

Ive got a 6hp suzuki outboard that simply wont run on 1 year old fuel. but i can put the same fuel in a (hired) fiat panda and itll run fine.

for the op, id say give it a go and see what happens, but check first that therre is no water in it, maybe drain a litre of two off the bottom of the tank and inspect it first?
 
SC35 said:
My real world experience is with a Mercury 5hp that refused to start and run on the previous season's fuel.
I took it in to a dealer, who ditched the fuel, put in fresh fuel, and it started on the second pull.
I think heat is also a factor ... the petrol can was stored in the cockpit where it got quite warm, and the more volatile components probably disappeared.
Click to expand...

Oops, I forgot to mention heat!

The fuel shelf life estimates I quoted are based on an ambient temperature of 20degC. At 30degC, the reduction can be fairly drastic being anything up to half the time for the same level of evaporation of the volatile compounds. The hotter it gets, the faster if evaporates (until it gets *really* hot and goes boom :D )
 
I can still remember the smell of stale petrol in ship’s lifeboats trying to start them in Glasgow docks in winter nearly sixty years ago as a teenager so yes but that fuel could have been in the tanks since the war and Boer at that
 
In a vented tank on a boat. Yes absolutely. BP say within 5 weeks as the volatiles evaporate your fuel will be 5 % heavier leading to a higher octane reading, (think pre-detonation), and a heavier fuel air mix leading to a equivalent air fuel ratio at constant volume closer to 12: 1 than 14:1 (think richer, plug fouling, bore washing). The longer the worse it gets.
So will it burn, of course yes. Is it what your engine was designed to run, of course no.
In a sealed metal container it will last 1 year. Once the seal is broken (even if the cap is screwed back on) then 6months at 20C or 3 months at 30 before it should be discarded.
 
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In the classic world we add fuel stabilisers over the winter lay up period
They start better and as Bruce says it better for the engine .

Theres issues with evaporation in carbs and gumming up , so you add this stuff and run it through .Reckons to prevent this .

It seems to work .

Also I have a strimmer that does not like it’s 2T left in the tank over the winter .Makes great weed killer btw - old ready mixed 2T .
Fresh fuel and it off 2/3 pulls .Old fuel won’t start after it’s lay up Nov to May .
 
BruceK said:
In a vented tank on a boat. Yes absolutely. BP say within 5 weeks as the volatiles evaporate your fuel will be 5 % heavier leading to a higher octane reading, (think pre-detonation), and a heavier fuel air mix leading to a equivalent air fuel ratio at constant volume closer to 12: 1 than 14:1 (think richer, plug fouling, bore washing). The longer the worse it gets.
So will it burn, of course yes. Is it what your engine was designed to run, of course no.
In a sealed metal container it will last 1 year. Once the seal is broken (even if the cap is screwed back on) then 6months at 20C or 3 months at 30 before it should be discarded.
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What nonsense. As I said some one would come along with a load of theory. Listen to those with real world experiences

Also I wonder how these theory mongers would discard 200 + ltrs of petrol
 
Your engine might run but that doesn't mean damage isn't being done. As any old motorbike owner will tell you using old fuel generally requires a carb rebuild.
 
Some real world experiences as requested:
Owned several straight 6 and 8 cylinder petrol engined vehicles, ex military, Rolls Royce b series engines. Designed to run on low octane pool fuel, including 2 star low octane petrol, approved to run on unleaded fuel.
After storing over winter, always needed topping up with fresh petrol otherwise they would misfire and generally run rough, always left minimal fuel in tanks over winter so it didn’t need much to top up and freshen fuel. Spark plugs would foul easilywith stale fuel, 8 cylinder engine was always more susceptible to this, I put that down to being a single carburettor and a long inlet manifold resulting in poor fuel distribution to individual cylinders. Never blocked the carburettor jets, I think the holes were too large!
I think Bruce is correct in that the octane increased over time as these engines were designed for low octane fuel. Some people found improvements adding paraffin to the petrol, that decreases the octane level. Never had an issue with pinking, possibly due to the ignition timing being after tdc, not before.
Collected several vehicles from a dealer that had stood for many years, some of the fuel had really gone off, smelt awful, actually burnt your skin if you got too much on your hand. Left black sticky solid lumps in bottom of fuel tank, really difficult to get off. This was found in a few of the vehicles, not all so I think it is dependant on several factors, temperature, moisture etc.
 
I have a 5 litre can of petrol sat on my doorstep, brought back from the boat a week or so back, that has definitely gone off. Not sure how to dispose of it.
Free to anyone who can pick up from Exeter, bigplumb, any interest?
 
I am planning on boating over winter on the clear calm winter days, with the introduction of e10 is it best to keep the tanks low and just put enough fuel in for the expected use on those clear calm days ?
Sorry for highjacking the thread but both fuels deteriorate e10 more so especially when water is present I believe.
 
longjohnsilver said:
I have a 5 litre can of petrol sat on my doorstep, brought back from the boat a week or so back, that has definitely gone off. Not sure how to dispose of it.
Free to anyone who can pick up from Exeter, bigplumb, any interest?
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And there in lies the issue. Imagine if it were not just a 5 ltr can which is difficult enough but it were over 200 ltrs in more than one boat. Do you honestly think people who are in such a situation empty their tanks and drain their systems of fuel every winter.

Re your 5 ltrs Most people of course would get rid of it illegally and in an environmentally bad way. Will you do the same I wonder ?.

As I say many times more interested in the real world and what people actually do rather than the theory.

Perhaps you could post a little report or indeed video of your method of disposing of your 5 ltrs.
 
Martxer said:
I am planning on boating over winter on the clear calm winter days, with the introduction of e10 is it best to keep the tanks low and just put enough fuel in for the expected use on those clear calm days ?
Sorry for highjacking the thread but both fuels deteriorate e10 more so especially when water is present I believe.
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Many people plan to boat over winter and some do but it is likely to be far less than you think so I would advise to just buy the Premium Petrol. Some can be E5 but some has no ethanol at all. Or just carry on as you have been. If you believed all the theory spouted you would never do anything. and then when you were sat at home scratching your bum the sky would fall in on your head
 
Bigplumbs said:
And there in lies the issue. Imagine if it were not just a 5 ltr can which is difficult enough but it were over 200 ltrs in more than one boat. Do you honestly think people who are in such a situation empty their tanks and drain their systems of fuel every winter.

Re your 5 ltrs Most people of course would get rid of it illegally and in an environmentally bad way. Will you do the same I wonder ?.

As I say many times more interested in the real world and what people actually do rather than the theory.

Perhaps you could post a little report or indeed video of your method of disposing of your 5 ltrs.
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To answer your questions, no and no.
 
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