DAYTONA BEACH -- When the green flag drops for the 53rd Daytona 500 today, most eyes will be on the action on the track. Those paying close attention to the flag, though, will notice something new -- a large "E" -- representing American Ethanol, the industry group pushing for expanded use of the biofuel. About 120,000 race fans will wave smaller versions of the same flag, handed out by NASCAR to promote its decision to switch fuels this year. Every car and truck in NASCAR's top three series in 2011 will use Sunoco Green E15 -- a blend of gasoline...