It seems you won't have to worry too much about it because most stations likely won't have it for quite a long time and by then it will probably be moot anyway.
E15 fuel is available only "at a few thousand pumps today," but said the U.S. will invest $100 million in biofuel infrastructure. E15 gas is currently available at about 2,300 fueling stations, according to the Department of Energy.
Even Uncle Sen. Chucky G is happy about it (read his Twitter posts) because it will make all his farmers happy and even the last guy ordered it available year round but the courts shut it down and even The Supremes refused to hear it so it can't be all bad.
