Gas Type by Car: Regular, Premium, Diesel or E85 / Mercedes-Benz / GLK-ClassMercedes-Benz GLK-Class Gas type by year YearGas type2015Depends on engine: diesel or premium2014Depends on engine: diesel or premium2013Depends on engine: diesel or premium2012Premium2011Premium2010Premium Source: U.S. EPA / DOE fuel economy data (fueleconomy.gov).