concept carCrocefficientfuelgasgreen cargreen techmpgmphshoeSpirauglyvehicleSpira foam car gets 100 mpg, is light enough to lift, and even floatsKevin HallFriday, May 15, 2009 - 4:12am However you feel about Crocs — which are amazingly ugly shoes and the inspiration for designer Lon Ballard's Spira — it's hard to say no to a car that manages 100 miles to the gallon and has a respectable top...