Indy cars use Methanol Alcohol not Ethanol. Totally different fuel with lots more BTU. Also dragsters use a blend of Methanol and Nitro.
Every car and Motorcycle I have had gets 10-15% less gas mileage on ethanol blended gasoline. In the summer we can buy pure gas in Wisconsin in some grades and vendors, in Florida we have a hard time finding pure gas as they passed a law where ethanol has to be used.
Actually they moved to ethanol in 2007 http://en.wikipedia.org/wiki/IndyCar_Series#Ethanol.