Many areas in the northeast are making the switch from reformulated unleaded gas with MTBE which was better for the air but was bad for the water to unleaded with 10% .
In Washington we do not have a choice. The regular winter formulation is 10% Ethanol. The summer formulation is Regular unleaded. I have not been able to attribute any MPG difference.
Here in Cali we have 10% ethanol year around now, at least it's not MTBE, which ruins engines in addition to the water table.
