Gas Type by Car: Regular, Premium, Diesel or E85 / Bentley / Continental GT ConvertibleBentley Continental GT Convertible Gas type by year YearGas type2020Premium2018Premium2017Premium2016Premium2015Premium (flex-fuel E85 engine available)2014Premium (flex-fuel E85 engine available) Source: U.S. EPA / DOE fuel economy data (fueleconomy.gov).