Ethanol is both corrosive as well as hydrophilic (attracts and absorbs water). Manufacturers can ensure that the fuel line, fuel tank, fuel pump, seals and gaskets are compatible with a fuel mixture that includes ethanol (up to 85% ethanol in E85 summer blend.) It is the water that eventually mixes with the ethanol that can cause fuel separation and break down of the fuel. The Volt has a stainless steel fuel tank so it will not corrode. The fuel system is sealed and pressurized so no outside air or moisture can normally get into the fuel tank.
The reason the Volt's fuel system is pressurized has to do with minimizing, detecting fuel vapor leaks. To qualify as a partial zero emission vehicle (PZEV) in California and other CARB compliant states the fuel system vapors need to be contained, any leaks detected. Because the fuel system is sealed the lighter, more volatile, hydrocarbons in the fuel mixture can't evaporate out of the fuel, into the tank and eventually pollute the outside air. If the fuel system won't hold pressure, most likely due to an improperly closed fuel cap or a failed fuel cap gasket the vehicle will detect the loss of fuel system pressure and indicate a problem with the fuel system. This would show up during a vehicle emissions test readout from the vehicle's computer memory.
It is a happy coincidence that the Volt's pressurized fuel system, designed to minimize gasoline vapors from escaping and polluting the air, enables fuel to remain in the fuel tank, for up to 12 months, before it must be used. The Owner's Manual states that only TOP TIER detergent gasoline be used in the Volt. If TOP TIER detergent gasoline is not available one bottle of GM Fuel System Treatment Cleaner added to the fuel tank at every oil change, can help. GM Fuel System Treatment Cleaner (available from your dealer) is the only gasoline additive recommended by General Motors.