Ethanol producers, ahead of the federally mandated schedule to produce 15 billion gallons of ethanol for use in U.S. vehicles by 2015, are lobbying the government to overturn the long-standing Environmental Protection Agency rule that limits ethanol/gasoline blends to 10% ethanol nationwide. Despite a recent ethanol downturn thanks to lower oil prices, officials with the Renewable Fuels Assn. say the industry could sell plenty of additional ethanol.