The 2017 Mercedes-Benz GLS 450 is available as a 4-door, 7-seat sport utility. Starting at $68,700, the 2017 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 22-mpg on the highway.