The 2020 Mercedes-Benz GLS 450 is available as a 4-door, 7-seat sport utility. Starting at $75,950, the 2020 Mercedes-Benz GLS 450 GLS 450 is powered by a 3.0L, 6-cylinder engine mated to an automatic transmission that returns an EPA estimated 19-mpg in the city and 23-mpg on the highway.