Maybe with the 9-speed tranny and RWD we might get published mpg of 33 fwy (or by taking e.g., 700 pounds off the rig with the use of more aluminum) but...
2017 Mercedes-Benz GLE 300d SUV 7-speed automatic transmission with 4MATIC all-wheel drive--
City mpg: 22
Highway mpg: 29
(Actual rating will vary with options, driving conditions, habits and vehicle condition.)
I do however get >29 fwy mpg with the 250 BTC which also is configured as above (29 mpg overall)