Any gas with ethanol really should be drained. It has been proven that the E10 gas (mandated by the state) sucks up moisture and when left sitting for more than 2 weeks can have water in your fuel. This crud gas has screwed up a lot of engines. Whenever possible use a premium gas without ethanol.
I knew it wasn't great when my mileage dropped in my truck, but I really didn't know the extent of the problems ehtanol laced fuel caused until an episode of Oregon Field Guide.
http://www.opb.org/programs/ofg/segments/view/1738