For this, we'd suggest you please visit the nearest authorized dealership as they would be able to assist you. Follow the link and select your city accordingly for dealership details.
The Mercedes-Benz GLS has 1 Diesel Engine of and 2 Petrol Engine of on offer. The Diesel engine is 2925 cc while the Petrol engine is 2999 cc (M256M) and 3982 cc (M177).