The more efficient unit is good for 603bhp in other applications, like the AMG E 63 S, but the biggest improvements over the 5.5-litre come with efficiency and its lighter weight, which should lend to more responsive handling.
AMG's current GLE model is no slouch, accelerating from zero to 62mph in 4.2sec, so its more potent and lighter successor could edge this heavyweight's sprint time into the realms of proper supercars. Its archrival, the BMW X5 M, is due on roads later this year with 592bhp, ensuring close competition.
The GLE 63 is expected to arrive a little later, likely in the early parts of 2019 at a US motor show, becuse the model is built in America. The regular GLE is due at the Paris motor show this autumn, suggesting AMG could launch its version in New York during the following spring.
Design changes for the GLE will mix the muscular bodyshape of the current car with the sharper, more streamlined features of Mercedes's latest design language. Most obvious on the recently spotted test car are the GLE's new headlights. The development car, a GLE 63, is also wearing a Panamerica front grille, linking it to other AMG models such as the GT sports car, which the grille was first featured on.
Further back, the car gets new wheel arch lips, giving it a more rugged stance and suggest its track could be slightly wider to enhance stability and grip. The GLE 63 will get a bespoke track and geometry setup designed specifically for its performance capabilities.
The GLE's wheelbase is expected to stretch slightly - the test car backs this as it looks to have a shorter front overhang. This would lend itself to better legroom inside, particularly in the back, which is a key trait to enhance the car's success in China.
At the rear, the window is more raked than the current model to create a more sporting stance. The GLE 63 will get a rear roof spoiler to help clean the flow of air that passes over the car.
The current regular GLE - codenamed W166 - made its debut in 2015, and this successor, the W167, will continue to compete with the likes of the Porsche Macan and the recently facelifted Range Rover Sport.
It will be joined by a new GLE Coupé model that uses the same running gear but features a sleeker roofline, offering a more direct alternative to the BMW X6. The limited-run Range Rover Coupé is also in this class, but it's £240,000 price-tag makes it a unique proposition.
As for powertrains for the non-AMG range, an updated list of turbocharged four- and six-cylinder petrol and diesel engines, as well as a new plug-in hybrid option, are expected. The latter is important to ensure the car can conform to strict emissions legislations in key markets, including China, which dictate that a car must be capable of zero-emission running.