After reading all the questions about should you use fuel stabilizer or not this is a little clip ......
I know what you're thinking. This stuff was stored in the ground, admittedly in unrefined form, for millions of years without losing its potency, but once topside it's got the shelf life of a tomato? Doubtless the risk of gas going stale is often exaggerated. Still, no getting around one basic truth: in principle gas can go bad.
The shelf life of gasoline depends on the type of gas and the storage conditions and can range from a couple months to a couple years. One wild card is that gas you buy at the pump may already have been in storage for anywhere from days to months.
What makes gas go stale? Usually the first thing that happens is the lighter chemicals in it evaporate, leaving behind a heavier, less peppy product. Gasoline is an ideal motor vehicle fuel partly because it vaporizes readily to form a combustible mix with air. If it sits unused, however, its more volatile components waft away, leading to poorer engine performance. It's hard to tell how much punch your gas has lost without scientific testing, but don't worry–though your car might start a little harder, it'll still run (assuming it ran before), and there's little risk in burning the fuel if this is all that's gone wrong.
The second cause of bad gas is oxidation–some of the hydrocarbons in the fuel react with oxygen to produce new compounds, almost all of them worse than what you started with. When oxidation becomes a problem, you'll know it without lab tests--the gasoline gives off a sour odor. If you pour some into a glass container, you'll see it's turned dark, and you might find small, solid particles of gum. Using oxidized gasoline is a bad idea, since the gum can clog your fuel filter, create deposits in your fuel system (especially the injectors), and generally hurt performance.
Finally there's the problem of contamination. Water, which can cause gas-line freezing and other problems, is the main culprit--it usually gets into stored gas via condensation as temperatures fluctuate. If the gas is relatively fresh, a "fuel dryer" additive (basically isopropyl alcohol) can help by combining with the water to make a burnable mix that can be run through the system. Another potential problem caused by water is bacteria, although that's not nearly as common. Gas contaminated with dirt or rust is a no go, as the crud will foul your engine.
I found. Basically you have 6 months to a year.