Gas Type by Car: Regular, Premium, Diesel or E85 / Chevrolet / HHRChevrolet HHR Gas type by year YearGas type2011Regular (flex-fuel E85 engine available)2010Regular (flex-fuel E85 engine available)2009Regular (flex-fuel E85 engine available)2008Depends on engine: regular or premium2007Depends on engine: regular or premium2006Regular Source: U.S. EPA / DOE fuel economy data (fueleconomy.gov).