Gas Type by Car: Regular, Premium, Diesel or E85 / Chevrolet / Monte CarloChevrolet Monte Carlo Gas type by year YearGas type2007Depends on engine: regular or premium (flex-fuel E85 engine available)2006Depends on engine: regular or premium (flex-fuel E85 engine available)2005Depends on engine: regular or premium2004Depends on engine: regular or premium2003Regular2002Regular2001Regular Source: U.S. EPA / DOE fuel economy data (fueleconomy.gov).