Condensation, there's moisture in the air, it absorbs water 50% faster then non ethanol fuel, the ethanol can cause phase separation in the tank in short it's a big problem that doesn't need to exist by completely eliminating the use of ethanol fuel ANYWHERE. Marinas offer ethanol free gas at their pumps to help keep boat owners from suffering from ethanol gas issues. Also you have to replace fuel lines that are approved for ethanol fuel, it will flat out dissolve a gas line that doesn't have the correct liner. It is a solvent that can loosen crud in a fuel systems, the tiny jets in the primary circuit of a emission approved carb are more susceptible to these particles. A carb'd motor on small engines be outboard motor or a weed trimmer doesn't need a EMC, computer, to run the fuel system, the ecm if equipped can control timing on that engine, so good clean fuel and maintaining/ using the motor is the best practice. To the OP, use your E10 pump gas , shy from E15 if offered in your state, some Stabil will work great, start it, run it routinely, and you'll be fine as far as fuel goes,,,gregg