Lets say that someone wants to store petrol in a garage (or anywhere else). How long can he keep it without losing its quality?
I mean : does the petrol modify itself with time or is it a "very long conservation" product?

I believe that it takes several years, at least. Cycling through it would help, keeping it from getting too old would help, but the primary concern would be storing it safely.

when all petrol is away ,SG-N has still lots of barrels in his garage :D
a nice slogan would be : buy or die !
anyway ,good idea ;)

You will have to call me "Emir SG-N" in a few years! :D

Hydrocarbon is stable, only over thousand of year from background radiation would the gasoline polymerize. More likely you would lose the gasoline from vaporization if the container were not sealed fully. I don’t know about the decay properties of the additives like MTBE.

IM sure I read a while ago that more than a few, say six months isnt very good, since it kind of separates out, and if your container isnt perfectly sealed, you lose the more volatile fractions which increases viscocity and probably affects combustion behaviour. On the other hand in every day use your unlikely to notice that much of a difference. But were it really cold for example.

I don't know the process that causes it, but gasoline will "go bad"
after a few months. I have had it happen to gas (petrol) in the
tank of a motorcycle I once owned. You can remove the cap on
gastank and smell of the gas itself has changed.

yeah, thats the evaporation of the lighter fractions I mentioned. Your gas tank isnt totally sealed.
And remember, theres benzene in petrol, try not to breath too much of it.

Chevron has this bulletin (http://www.chevron.com/prodserv/fuels/bulletin/longterm_gasoline/) on long-term storage of gasoline. Lots of good info.

Thanks Iris! (and thanks to the others too!)