An unusual coalition has been formed in Washington in an attempt to kill a creature of Washington: corn ethanol. The oil industry, environmentalists, taxpayer groups, livestock growers and foreign aid groups all want Congress to repeal the mandate requiring a 15 percent blend of ethanol in gasoline, after a federal court upheld the rule last week. More than 40 percent of the U.S. corn crop goes to ethanol, combining with a continuing Midwest drought to drive up corn prices. In a conference call Monday, refiners said it wrecks everything from car engines to outboard motors to chain saws.