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The 2021 Mercedes-AMG GLS63 Has 603 HP, 7 Seats, and No Chill

This über-family hauler is as deliciously unhinged as ever.

If you can believe it, when there's a need to combine seven-passenger seating capacity with sports car speed, there actually is an embarrassment of choices. You could buy a Dodge Durango SRT, or a (previous-generation) Mercedes-AMG E63 S station wagon, from before Mercedes nixed that car's third-row seat option. Or, if you want the mack-daddiest of them all, consider the latest Mercedes-AMG GLS63. 

The very large and equally luxurious AMG-ified GLS-class packs the same brawny electrically assisted 4.0-liter twin-turbo V-8 that's used by the equally new 2021 GLE63. A 48-volt starter-generator motor zaps the V-8 with an extra 21 hp and 184 lb-ft of torque. The result? 603 hp and 627 lb-ft combined. (That horsepower figure, by the way, matches that of the E63 wagon, which does without the electrification.) But power isn't the only benefit. Fuel economy is improved as well, as the 48-volt system controls the engine's start-stop function and idle speed. But you probably don't care about that, and neither, we suspect, do many would-be GLS63 buyers. They will care about Mercedes' estimated zero-to-60-mph time of 4.1 seconds and top speed of 174 mph. If those estimates turn out to be accurate, the Mercedes-AMG GLS63 will become the quickest three-row SUV in the world—at least until the Alpina-tuned BMW X7 emerges to test its mettle.

All of the GLS63's power shoves its way through a nine-speed automatic transmission on its way to all four tires via AMG's 4MATIC+ all-wheel-drive system. The "+" indicates that this version of 4Matic can vary the torque distribution between the front and rear axles between 0:100 and 50:50 ratios, meaning it can send 100 percent of engine torque to the rear axle if necessary. That's key, because AMG worked hard to give the GLS63 rear-wheel-drive dynamic characteristics; all-wheel-drive traction remains a blink away if it's needed for extra traction and going faster. An electronic locking differential on the rear axle boosts the big SUV's sporty rear-drive sensations.

Suspension dynamics and ride quality also benefit from the 48-volt electrical system, as it powers the suspension's electro-mechanical actuators and stabilizers which mitigate bump harshness body lean in corners. With its active and height-adjustable air suspension, the SUV aims to balance comfort, agility, and off-road capability. Curiously, the GLS63 does not receive the same E-Active Body Control hydraulic dampers that help standard GLS models "bounce" their way out of low-traction or sandy terrain should they get stuck.

The GLS63 might not be capable of hump-bouncing its way out of shale, but it does include a sand-focused drive mode. There also are trail, comfort, Sport, and Sport+ modes. Why so many options? Who cares? Does the GLS need 603 horsepower? No, but this is a Mercedes-AMG—luxury and unnecessary widgets are par for the course, even if you'll never see one of these swanky SUVs bashing through your local off-road park or, more to the point of the AMG, drifting around corners with its rear tires smoking like a California fire. 

Appropriately for its baseline luxury mission, the GLS' interior remains opulent. There is a front-seat massage function and available seat heating in all three rows, along with a Burmester sound system and 64-color ambient lighting feature. However, to play up the AMG raciness, the front seats gain deep bolsters to provide better support, and the AMG-specific steering wheel has a spicy flat bottom and enlarged metal shift paddles. Between the steering wheel's spokes are drive-mode controls with miniature displays, which the driver can use to dial in various vehicle settings. Carbon-fiber trim is, of course, optional. 

Just like in the more comfort-oriented GLS-class grades, the GLS450 and GLS580, the GLS63 uses Mercedes' latest MBUX operating system for its dual 12.3-inch digital displays. Both have been modified to support AMG-specific readouts, which can be set up to emphasize engine revs, g-forces, or lap times. Other AMG touches extend to the GLS63's exterior, although they're subtle.  An imposing vertical-slat grille is central to the aerodynamically enhanced front fascia, while quad exhaust outlets profess the engine's power out back. Beneath standard 21-inch or available 23-inch wheels are ventilated and drilled brake rotors measuring 15.7 inches in front (clamped by six-piston calipers) and 14.6 inches in back. 

Is any of this necessary? Hardly. But can you go 174 mph in a minivan or some "regular" three-row crossover? Hell no. There may be a surprising number of high-horsepower, ultra-quick three-row SUVs, but the redesigned Mercedes-AMG GLS63 continues to tower above them all.