Introduction

Introduced for the 2017 model year, the full-size GLS SUV served as a successor to Mercedes-Benz's GL-Class model. Apart from a new front end, the still-boxy GLS differed little from its GL predecessor. 

Unchanged for 2018 except for an additional 19-inch wheel choice, the GLS carries on its traditional, old-school approach to SUV design. Rather than attempt to conceal its squarish profile, the GLS appears to relish its role as a delightfully charming three-row people-carrier. 

A new trim level will be available in summer 2018: The Grand Edition will offer high-end leather interiors and unique 20-inch wheels. 

Mercedes-Benz offers three models: GLS 450 with a V6, GLS 550 with V8 power, and high-performance Mercedes-AMG GLS 63, packing a 577-horsepower twin-turbo V8 that issues 561 pound-feet of torque. 

All-wheel drive is standard on all three. 

In the GLS 450, the twin-turbo 3.0-liter V6 develops 362 horsepower, driving a 9-speed automatic transmission that's ready to deliver brisk acceleration. The same 9-speed transmission serves the GLS 550, whose 4.7-liter V8 generates 449 horsepower and 516 pound-feet of torque. 

To handle all the power of the 5.5-liter V8 in the AMG GLS 63, a tough 7-speed automatic is installed. Not many GLS buyers are likely to opt for the AMG variant, with its 4.5-second 0-60 mph acceleration time, but it's still a welcome addition to the lineup. 

No one is likely to be surprised by the GLS's impressive all-weather capability, or its overall cargo-hauling talents. Compensation for crosswinds is programmed into the GLS. The driver-attention monitor displays a coffee cup as a warning, when sensors determine that the driver may be getting drowsy. 

In addition to all the panache that's provided by Mercedes-Benz's big luxury SUV, the GLS boasts plenty of available safety technology. Forward-collision warning with automatic emergency braking is standard, along with a rearview camera. Safety options include blind-spot monitoring, adaptive cruise control with steering assist, active lane control, and traffic-sign-based speed warnings. 

Safety ratings are absent, because neither the National Highway Traffic Safety Administration nor the Insurance Institute for Highway Safety has crash-tested the GLS. 

Even though the GLS doesn't promise off-pavement prowess to rival Range Rover models, it can be fitted with such features as navigation, high-end audio, premium leather upholstery and wood trim, and an Off-Road package. On the infotainment front, Apple CarPlay and Android Auto are included. 

Lineup

The 2018 Mercedes-Benz GLS 450 ($69,550) comes with V6 engine, 4MATIC all-wheel drive, automatic climate control, power driver's seat, power tailgate, remote start, cruise control, COMAND infotainment interface with 8.4-inch display screen, and synthetic leather upholstery. (Prices are MSRP and do not include $995 destination charge.)

GLS 550 ($94,950) substitutes a 4.7-liter, 449-horsepower V8 for the V6 engine, adding 21-inch wheels. 

AMG GLS 63 ($125,300), the hottest performance, boasts a 577-horsepower V8, along with specific body components and wheels. 

Options for the GLS 450 include surround-view cameras, Bang & Olufsen audio, cooled front seats, heated power second-row seats, and a panoramic sunroof. An Off-Road package adds a reduction gear and locking center differential. 

Walkaround

While other SUVs feature curves and flowing surfaces, the GLS leans toward right angles. In profile, it has the look of a wagon, but it's less noticeable at any other angle. 

Up front, large LED headlights flank a huge Mercedes-Benz logo, tucked within a wide grille. Farther rearward, the squared-off GLS body is largely the same as that of its GL-Class predecessor. 

Depending upon the model, body details very. The GLS 550 wears flared wheel wells, above 21-inch rubber. The AMG GLS 63 gets a distinctive body kit. 

Interior

As many as seven adult passengers can ride in a GLS without feeling cramped. In every direction, space is abundant. Seating is flexible and trim ranks as opulent. Today's interior has a warmer feel than earlier models, with large wood panels and a big display screen atop the dashboard's center. 

Up front, seats are nicely bolstered and heated, power-adjustable in multiple directions. Options include seat cooling, adjustable bolsters, and four-mode massaging. 

Large door openings ease entry into the second row, where seats can be heated and powered. Three persons can occupy the middle row, though two would be more content. Second-row seats fold and slide out of the way, using either a handle or power button. Six-foot passengers can find comfort in the third row, once they reach that position. 

Behind the third row, cargo volume totals a modest 16 cubic feet. Folding that bench raises cargo space to 49.4 cubic feet. Second-row seats can also be folded down, for a total of 93.8 cubic feet. 

Large round digital gauges are separated by an information panel. A digital display for COMAND infotainment sits on the dashboard, but the system is cumbersome and confusing. 

Generally quiet and composed, the GLS permits little wind noise, despite its tall profile and large mirrors. 

Driving Impression

At a glance, the uninitiated observer might dismiss the immense GLS as one more oversize SUV. Instead, it warrants consideration for its powertrain selection, ride quality, and off-road capability. 

All three versions handle well, though the experience might feel a bit strange initially, due to the GLS's long, tall body and 8.5-inch ground clearance. Behaving with sport-wagon finesse, the GLS feels like a smaller vehicle, giving the driver a sense of being fully in charge. With standard wheels, the steering feels just about right: neither loose nor light. With variable-ratio steering, response differs at low speeds. 

Qualifying as an unabashed heavyweight, the GLS delivers a poised ride, typically buttery-smooth, as the air suspension subdues nearly all rough spots on the pavement. Optional low-profile tires could make the ride a tad jiggly. 

Adaptive anti-sway bars struggle to cope with shifting terrain ? a challenge with any tall, heavy vehicle. If installed, the optional Active Curve system presses down on anti-sway bars to counterbalance body lean. 

Acceleration ranges from strong to scalding, depending on model, though turbo lag may be noticed. The 9-speed transmission might feel excessively 'busy'? when entering a freeway ramp or conquering a steep, sharp corner. Selectable drive modes tailor traction systems as needed, while manipulating the steering, drivetrain, and adaptive suspension. 

Gas mileage wins little praise. The base GLS 450 is EPA-rated at 17/22 mpg City/Highway, or 19 mpg Combined. GLS 550 fuel economy falls to 14/19/16 mpg. The Mercedes-AMG GLS 63 is EPA-rated at a dismal 13/18 mpg City/Highway, or 15 mpg Combined. 

Summary

The Mercedes-Benz GLS competes against Range Rovers, Lexus LX, and Cadillac Escalade, so compelling features and premium-level details are the rule. The GLS checks all the boxes. It is equipped well, hauls passengers and cargo luxuriously, and offers excellent capability in all types of weather. 

Driving impressions by Marty Padgett, The Car Connection. James M. Flammang contributed to this report.