Open Fuel Act of 2017 This bill requires each fleet of a manufacturer of passenger automobiles (including light-duty motor vehicles) to be comprised of at least: 50% qualified vehicles in model year 2020, and 80% qualified vehicles in model year 2021 and each subsequent year. A "qualified vehicle" is: a vehicle that operates on natural gas, hydrogen, or biodiesel; a flexible fuel vehicle capable of operating on gasoline, E85, and M85; a plug-in electric drive vehicle; or a vehicle propelled solely by fuel cell or by something other than an internal combustion engine. The bill authorizes: (1) a manufacturer to request an exemption from such requirement for specified models, lines, and types of automobiles; and (2) the Department of Transportation to grant such an exemption upon determining that unavoidable events prevent the manufacturer from meeting its required production volume of qualified automobiles.