Gas Type by Car: Regular, Premium, Diesel or E85 / Cadillac / ATSCadillac ATS Gas type by year YearGas type2019Depends on engine: premium or regular2018Depends on engine: premium or regular2017Depends on engine: premium or regular2016Depends on engine: premium or regular2015Regular2014Regular2013Regular (flex-fuel E85 engine available) Source: U.S. EPA / DOE fuel economy data (fueleconomy.gov).