Truly, flex fuel in its purest sense would mean "It burns just about anything you can give it". A company in Iowa called Hydrogen Engine Center, Inc. have created an "industrial engine" that will bolt into various applications (kind of like CAT engines bolting into school buses, semis, etc.). This engine will presently burn hydrogen, ethanol, natural gas, propane, or digester gas from landfills. If we add electric/hybrid and bio-diesel to the mix…someone would have to create a new pricing software to calculate the best price alternative nation wide for all options at all times and deliver it to your inbox, cell phone, or via RSS feed. Hummmmm.