The 2021 Mercedes-Benz GLS 450 is available as a 4-door, 7-seat sport utility. Starting at $76,000, the 2021 Mercedes-Benz GLS 450 GLS 450 is powered by a 3.0LL , 6 - cylinder engine mated to an automatic transmission that returns an EPA estimated 20-mpg in the city and 24-mpg on the highway.