That's the ethanol-component of the gas (i.e. the E part of E5, E10), as it degrades. If you had pure gasoline, you could store it for years (and in past, coun

That's the ethanol-component of the gas (i.e. the E part of E5, E10), as it degrades. If you had pure gasoline, you could store it for years (and in past, countries and armies did exactly that for their reserves).