The 2018 Mercedes-Benz GLS 450 is available as a 4-door, 7-seat sport utility. Starting at $69,550, the 2018 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 17-mpg in the city and 22-mpg on the highway.