How long before petrol "goes off"?

[LandingSpot]

How long would you expect half a tank of unleaded (specifically VPower) to be OK for before it would no longer run an engine?

My petrol lawnmower (for racing you understand!) wouldn't start after a few months of non use even when loaded with some unleaded from a sealed jerry can from the shed. Got some new stuff and away she went! 2hp ftw!!

So how long before your 50quid of VPower is worthless??

[Astra Dan]

I got a Pug 205GTi started after 4 years with just a new battery.
Obviously I'm not saying it hadn't lost some of it's potency after that long, but it's certainly OK to run an engine.

[paul.deitch]

Goes "off" ie loses a lot of its volatile components after about six weeks in a vented tank. Will eventually go gummy if left long enough.

[bill bob]

Hi,
I SORN my kit car through the winter months, (November to March) without any noticable problems with petrol degradation.

I recently got an old lawn mower out which had been in the back of the shed for nearly 4 years and the carb was all gummed up with a waxy lacquer which smelled putred. I had to wash it out with thinners to get rid of it. Having done that and filling it up with fresh petrol, it started second pull.

So the answer to the question must be somewhere between 5 months and nearly 4 years.

regards
Bill Bob

[GC8]

Optimax/V-Power loses its octane rating relatively quickly. Thats why it leaves the refinery at over 100RON and why you shouldnt buy it from a garage which has a low turnover of SUL.

Petrol itself doesnt stop working though, certainly not in my esperience. Ive used petrol thats been stored in cans for several years, in cars which dont require 99RON fuel, and theyve run perfectly well.

[andy-xr]

Have done 3 years before with no noticeable difference really. As long as it's sealed it should be OK