Gas Type by Car: Regular, Premium, Diesel or E85 / Buick / EncoreBuick Encore Gas type by year YearGas type2026Regular (flex-fuel E85 engine available)2025Regular (flex-fuel E85 engine available)2024Regular2023Regular2022Regular2021Regular2020Regular2019Regular2018Regular2017Regular2016Regular2015Regular2014Regular2013Regular Source: U.S. EPA / DOE fuel economy data (fueleconomy.gov).