Sorry guys, but a lot of what has been written is not strictly correct. I work as an expert consultant to the oil industry, and am a member of the Institute of Petroleum, so I do know what I'm talking about.
The Reid Vapour Pressure (RVP) specification for gasoline referred to above is indeed adjusted seasonally to prevent possible vapour lock. In summer, when the fuel will be warmer, it is necessary to have a fuel with a lower RVP. In winter, it can be higher without causing a problem. Therefore, there is no problem using a summer grade in winter, but on a particularly hot day, there can be a chance of vapour lock with a winter grade fuel. This is dependant on a fuel delivery system, and the requirement to retain a NPSH (net positive suction head) The calculation of NPSH is a rather complex business, and it is dependant on the RVP amongst other things.
The vapour pressure is a function of the volatile components. Butane is the main volatile component in a modern gasoline, which for commercial reasons nowadays will almost certainly be a product known as RFG (reformulated gasoline). Ethanol is not particularly volatile, and hence has a low RVP. In Europe, Ethanol trades at about $500 per ton, and Butane about $250 ton. Simple economics dictates which product gasoline blenders use! European gasoline specs also specify a maximum of 14% alcohols in the blend (Ethanol is ethyl alcohol)
However Ethanol (and more usually methanol - Methyl alcohol) is used in gasoline in greater quantities in refining countries with plentiful access to ethanol and limited access to butane. This is generally 3rd world countries, where ethanol is typically produced from the fermentation of sugar beet.
However these materials will not meet European or US Gasoline specs.
With regards to ChrisVJ's point about gas deteriorating faster in plastic, it's true that butane molecules can more easily pass through plastic than tin. For that reason, plastic sample bottles are not generally used for volatile materials such as Gasoline. My job often involves analysis of samples weeks, months (or even years) after shipment, and gasoline samples stored in plastic bottles are useless for this purpose.
Chris is also correct that ethanol can adversly effect synthetic and natural rubber seals. I definately agree with his final comment - "put some nice gas in your plane and fly safe". Sound advice.