Introduction

The Mercedes-Benz GLS SUV, a three-row flagship, was until last year known as simply the GL, but the S was added to its name to raise its stature, make it sound more like the S-Class sedans, because Mercedes-Benz considers it to be the S-Class of SUVs. 

We think it's close, but not quite. Not even with 2017 changes to styling, cabin, infotainment, and powertrain, a new 9-speed automatic transmission intended to boost the fuel mileage a bit. 

We drove the new GLS in the Austrian Alps, where we found it to be relatively nimble in the tight curves, despite its size, nearly 17 feet long. Its ride is smooth on standard air suspension, and it handles like a much smaller vehicle. 

There are four models, three of them with 4MATIC all-wheel drive, each with a different engine: one diesel, one V6 and two V8s, all turbocharged. They are the GLS 350d 4MATIC, GLS 450 4MATIC, GLS 550 4MATIC, and the AMG GLS63 uber-performance sports SUV. 

The GLS 350d uses a 3.0-liter V6 turbodiesel making 255 horsepower and 455 pound-feet of torque. The GLS 450 uses a twin-turbocharged 3.0-liter V6 making 362 hp and 369 lb-ft. The GLS 550 uses a 4.7-liter twin-turbo V8 making 449 horsepower and 516 pound-feet; it's the tow master of the line, if not the class. And if you want to give six young soccer players a real thrill, pack them into the 577-horsepower AMG GLS 63, and hammer the throttle so they can feel 561 pound-feet of torque under their butts, and hear the howl of its 5.5-liter twin-turbo V8. 

There is an available offroad package that raises the ground clearance from 8.5 to 12.0 inches. So it can look brutal: way big and way high. 

The GLS offers room in all three rows, a rare thing with any SUV; in fact, two six-footers can fit in the third-row seat, with adequate headroom and legroom, although it will take some agility to get back there. The 50/50 third row folds on each side with the push of a power button, and when the second row is also folded (manual or power), there's almost as much cargo space as a Cadillac Escalade with long wheelbase. 

The GLS350d, with its diesel engine, gets the best mileage of the models, EPA-rated at 22 miles per gallon Combined city and highway. The GLS450 with its V6 gets 17/22/19 mpg City/Highway/Combined. The GLS550 with its V8 is rated 14/18/16 mpg, and the AMG GLS63 gets just 14 miles per gallon Combined, but what do you expect with 577 humongous horsepower?

The government and insurance industry haven't crash-tested the GLS because of its low volume, but there's little doubt that it won't come out ahead in a crash with another vehicle, or maybe even a brick wall. Standard safety equipment includes six airbags in front, side curtain airbags extending to the third row, and the Collision Prevention Assist Plus program, that warns the driver of a possible crash with an object ahead, and applies the brakes if the driver doesn't respond quickly enough. 

Lineup

The 2017 Mercedes-Benz GLS includes the GLS350d, GLS450, GLS550, AMG GLS63. 

Optional safety systems include Active Blind-Spot Assist, Active Lane Keeping Assist that tugs on the steering wheel when sensors think you're wandering, and automatic braking for pedestrians you might miss. 

Optional opulent features include heated and cooled cupholders, ventilated front seats, designo leather upholstery, and Harman/Kardon or Bang & Olufsen sound systems. 

Walkaround

The 2017 change to the face of the GLS makes it look bolder, with a wider grille with two bars that look like a biplane wing, a bigger three-point star emblem, racier air dam, two long power bulges on the hood, and more aggressively sculpted fenders. 

But it still looks dated, the same upright boxy shape with vertical tailgate that's been there for five years. At least the styling shows more class and less chrome than some luxury SUVs. 

The lights (front and rear), bumpers, and alloy wheels are also redesigned for 2017. Taillamps and DRLs are now LED. 

The GLS 550 has fender flares around 21-inch wheels, while the AMG GLS 63 has its own body pieces. There are exterior packages that add things like aprons, running boards, and side flaps that don't sound very Mercedes-like to us. 

Interior

The cabin of the GLS cavernous, comfortable, and almost as versatile as a minivan while being far more luxurious. The textures and trim are tops. The interior palette ranges from black leather with piano black dash to Ginger Beige and Espresso Brown. Lighter shades of leather and trim make the cabin feel more airy, as does the optional glass sunroof that's so big it extends over the rear seat. 

The instrument panel, console, steering wheel and display screen have been redesigned. The screen now rises from the dash like other Mercedes cars and SUVs. There are two large all-digital instruments behind the steering wheel, separated by a smaller info panel. The COMAND system infotainment knob is on the center console. The metal-trimmed vents stand out for their rectangularity, as most new vehicles have round vents nowadays. 

The front seats are supremely comfortable, with standard heat and eight-way power. Available comforts include four modes shiatsu-while-you-drive, from slow to fast and vigorous. 

Wide rear doors make it easy to climb in and out. The second row flips and folds with a feature called Easy Entry, either a manual handle or power actuator that's noisier than we would expect from a Mercedes. With the seats up there's only 16 cubic feet of cargo seat in back, but with the third-row down there's 49.4 cubic feet. 

With the 50/50 split power-folding third row of seats up, the GLS has a modest 16 cubic feet of cargo space. Flip them forward and that rises to 49.4 cubic feet, and with both rows folded there's a very spacious 93.8 cubic feet. 

The GLS is quiet inside at 70 mph, despite its blocky aerodynamics. Even the open sunroof doesn't add much wind noise. 

Driving Impression

The GLS is one of the most composed full-size SUVs on the planet. On the road, it doesn't feel 17 feet long, for sure. It feels almost like a C-Class sedan. Its standard Airmatic air suspension delivers a soft ride, better than the Escalade or any SUV with a live rear axle, and especially in Comfort, the default mode. 

In the parking lot, you'll know for sure it's 17 feet long. However its light steering makes it easy to maneuver, and its 40.7-foot turning circle is tight for its size. In the Austrian Alps, where we drove the new GLS, we could toss it around the climbing hairpin turns. There is some body roll, but there's an optional Active Curve system that electronically stiffens the front and rear anti-roll bars. We drove a model with this system, and found we preferred the GLS without it, because it felt more natural. 

We also prefer the standard 19-inch wheels and tires, rather than the big wheels with low-profile tires that add bounce. The variable-ratio steering on standard wheels and tires doesn't deliver a lot of feedback, but its resistance is about right. 

The three all-wheel-drive 4MATIC models use the new 9-speed automatic transmission, but the powerful AMG GLS63 needs the beefier and older 7-speed automatic. There's some turbo lag in all of the engines, and the 9-speed uses that lag time to kick down two or three gears when you floor it, for example on a freeway onramp. The tall ninth gear keeps the rpm below 2000 at freeway speeds. 

The Dynamic Select dial enables five drive modes. There's Comfort, Sport, Slippery (we like the name of that one), Off-Road, and Individual, to mix the functions to personal preferences. We think this last one is overkill, a bit complex for owners, and too precise because road surfaces change so quickly. 

The available Off-Road Engineering package adds a sixth mode, Off-Road+, with a locking center differential and additional reduction gear to enable a crawl over rocky ground. It also lifts the GLS to one foot of ground clearance. 

Comfort is the default mode, and it's a good one, for family trips and good fuel economy. But we loved Sport mode in the Alps; it gives a bunch more power, stiffens up the suspension, and makes the steering heavier and tighter. 

We used Slippery mode as well, facing some icy roads and snowy Tyrolean mountain trails. Our GLS was confident and sure-footed, running down hills at 25 to 35 mph in rutted snow, as the anti-lock brakes stopped the big SUV quickly. Thanks to its sophisticated electronics controlling the vehicle's power and traction delivery, the GLS will be safer in American winters than just about any vehicle we can think of. 

Summary

The Mercedes-Benz GLS is not without competitors for the crown of ultimate full-size luxury SUV, but when you look at each category, it's consistently up there. Four engine choices give it versatility, four entrants in sub-categories. We can't see any dealbreakers, except maybe price. 

Driving impressions by The Car Connection.