Petrol & Use-by dates

[CivicSi]

Quick question... A mate of mine tells me that petrol is only good for use for about 3 months.... i've never heard of this... is this true?

[dsp26]

generally true.. coz generally petrol loses ~1oct a week and goes stale...


also 3 months...?? someone losing their license?

***EDIT***
Disclaimer: I do not know the above as fact, but merely what many others have told me, i however have reason to believe it as per my Post#7 below regarding leaving my own vehicle after a certain time...

[CivicSi]

So how much octane can fuel loose before it is useless?

[SPEEDCORE]

generally true.. coz generally petrol loses ~1oct a week and goes stale...

That is interesting. When V8 Taxicars where using Shell Optimax as their controll fuel they where saying that it was stable enough to not drop more than 1 point in RON in 12 months, if stored in the right conditions.

If we are talking about fuel being left in a cars fuel tank or a canister of sorts then obviously that would most likely not be considered "right conditions".

Funnily enough, bought a lawn mower a few weeks ago and they said not to put fuel in the mower or store in a can for more than 3 months due to the same reason.

[CivicSi]

Lawn mower fuel would be different though? Not sure, could be wrong!

[Drew]

The fuel I have stored for my mower has been sitting for like a year, when ever I go to use it... Works just fine

And the Accord once sat for 6 months and it worked fine after that too

[dsp26]

lol off-topic.. are the mowers 2 stroke or 4 stroke?

2-stroke needs oil mixed in fuel so issue is sort of useless.... for cars it's different, having the faulty pcv valve leak oil into your intake then combustion chamber lowers octane rating too...

but i didn't think it'd matter for mowers coz their not as strict on octane rating.

fuel would actually burn easier the lower the octane rating... and the reason cars run on minimum 89oct RON is obviously the ping/detonation issue with the piston stroke cycle...



The octane rating is a measure of the autoignition resistance of gasoline or petrol and other fuels used in spark-ignition internal combustion engines. It is a measure of anti-detonation of a gasoline or fuel.

Octane number is the number which gives the percentage, by volume, of iso-octane in a mixture of iso-octane and normal heptane, that would have the same anti-knocking capacity as the fuel which is under consideration. For example, gasoline with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90.





And the Accord once sat for 6 months and it worked fine after that too
what year model is the accord though? coz i can almost guarantee that wouldn't be the case for older cars with junk in the tanks already... it is actually more evident especially on a turbo car tuned to say 98oct... leave it for 3months and it's goone...

i once left 98oct in my NX for a month (overseas holiday), the thing was base afpr tuned to run safe lean on about 95oct via dyno and the thing wouldn't idle properly when i got back...

off-fuel is one of those reasons i carry a bottle of octane booster in my boot for emergencies...

[SPEEDCORE]

The fuel I have stored for my mower has been sitting for like a year, when ever I go to use it... Works just fine

And the Accord once sat for 6 months and it worked fine after that too

The issue of the engine turning over and working is not the point dude. The point is if you are going to use old fuel where there has been degradation/denaturing and RON is down.... you run risk of big detonation if you start putting big load on the engine. Pretty much if you have let your car sit for a while, you are going to want to baby it until that fuel has gone, or at least topped up the tank with some fresh fuel. Even then I would go easy on it till that mixed tank was through.

dsp26: Yeah 4 stroke mower so no pre-mix, bastard is easier on the ears and nose too :).

[Drew]

4 strokers are for girls...

Mine is a 4 stroke =/

[SPEEDCORE]

So a heavier and more maintenance motor is for girls.... interesting train of thought.

[krogoth]

^lol

fuk 2 strokes, fuk 2 stroke bikes too

unless its an aprilla 125, lol

anyway, as long as the fuel is kept in a sealed container, full of fuel, then it should be more than fine for quite a bit of time

if the fuel isnt exposed to leaking air, it wont oxidise any were near as much, or something along those lines, im no chem buff

[SeverAMV]

dudes... fuel oxidising will improve complete combustion and hence power, fuel oxidising is considered a bump in octane with regards to labelling regulations. this is because it makes the mixtures slightly leaner, which improves combustion.

fuel shouldnt oxidise unless you've got a fair few additives in and a few unstable mixtures in your tank. otherwise its chemically improbable, if not impossible for the fuel to go 'off'. you need a reducing agent to be present with the fuel (or a crapload of air over a very long period in unstable high temp conditions) for the fuel to oxidise.

[krogoth]

as i said

im not chem buff, at all, lawll

but yeh, i think i agree with sever am

3months shoodnt be a problem

but i think the longer its left ther, the worse it will be overtime

[yfin]

generally true.. coz generally petrol loses ~1oct a week and goes stale...


1 octane per week! Where did you get that from as it is rubbish. Maybe if you put it in an unsealed container exposed to the environment.

RON will not significantly change in a relatively sealed environment. Shell says 6 months.