The data indicates that all observed models of the Mercedes-Benz S Class (2017-20) S350L 4DR Saloon with the specified trim and specifications are equipped exclusively with a 2.9-litre diesel engine. This engine capacity accounts for 100% of the sample, and the vehicles uniformly use diesel as their primary fuel type, also at 100%. This suggests a consistent engine and fuel configuration across this model range, reflecting standard factory specifications for this vehicle.