There is another thread to this topic in the "fuels and emissions" where Adam's Apple covers much the same ground.
The one time to re-consider your fuel choice is putting it away for the winter. Up here, only the highest octane is without any ethanol (marked right on the pump). "Carb defender" is on the market to help reduce the effects but articles in http://www.powerperformancenews.com/ suggest fresh gas with ethanol (ie driving it) is not a problem. Leaving it sit where the ethanol attracts the water and causes corrosion is. Suggestion is to fill it to the neck to minimize the available area or drain the tank.
I'm not a fan of either since gas breaks down over time and I don't really want a tank full stale gas in the spring. Draining it entirely leaves things entirely exposed too. So, my plan is to add fresh gas without ethanol when it gets warmed up regularly over the winter, trying to freshly pickle it each time.
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