Before we get too far, we must offer a caveat: As of press time, the Mercedes-Benz GLS350d has not received a certificate of compliance from the all-powerful U.S. Environmental Protection Agency. Thanks to increased scrutiny of diesel-powered cars, trucks, and SUVs, the due-for-2017 GLS350d is not yet on sale at U.S. Nevertheless, when the company invited us to sample all its fullsize-SUV wares, we leapt at the opportunity. Nestled in a fleet of fire-spitting Mercedes-AMG GLS63 and G65 SUVs was the object of our oil-burning affection, the GLS350d. Photo 2/14 | Mercedes-Benz鈥檚 invitiation included opportunities to drive each version of the G and GLS SUV for a few days, including the mighty, twin-turbo 6.0L V-12-powered Mercedes-AMG G65. Although we were here for the diesel, it was still tough to give the 621hp SUV鈥檚 keys back. Mercedes renamed its largest SUV (formerly known as the GL-Class) the GLS for the 鈥?7 model year, adding the extra letter to denote its relation to the S-Class sedan. Furthermore, if/when the diesel engine gets certified by the Feds, it will no longer wear a 鈥淏luetec鈥?badge on its rear haunches, eschewing the trademark for a subtle 鈥渄 鈥?suffix on the model name.

Before we get too far, we must offer a caveat: As of press time, the Mercedes-Benz GLS350d has not received a certificate of compliance from the all-powerful U.S. Environmental Protection Agency. Thanks to increased scrutiny of diesel-powered cars, trucks, and SUVs, the due-for-2017 GLS350d is not yet on sale at U.S. Nevertheless, when the company invited us to sample all its fullsize-SUV wares, we leapt at the opportunity. Nestled in a fleet of fire-spitting Mercedes-AMG GLS63 and G65 SUVs was the object of our oil-burning affection, the GLS350d. Photo 2/14 | Mercedes-Benz鈥檚 invitiation included opportunities to drive each version of the G and GLS SUV for a few days, including the mighty, twin-turbo 6.0L V-12-powered Mercedes-AMG G65. Although we were here for the diesel, it was still tough to give the 621hp SUV鈥檚 keys back. Mercedes renamed its largest SUV (formerly known as the GL-Class) the GLS for the 鈥?7 model year, adding the extra letter to denote its relation to the S-Class sedan. Furthermore, if/when the diesel engine gets certified by the Feds, it will no longer wear a 鈥淏luetec鈥?badge on its rear haunches, eschewing the trademark for a subtle 鈥渄鈥?suffix on the model name.

Photo 4/14 | Updated front-end styling includes changes made to give the GLS a familial resemblance to other modern Mercedes-Benz vehicles. The rounded front grille, reshaped headlamps, and restyled LED light pipes look similar to those on the current C-Class, E-Class, and S-Class sedans. Key exterior alterations include an updated front fascia with a new grille and headlamps that bring the GLS in line with its S-Class sibling. Around back, restyled LED taillights keep those behind you abreast of the goings-on, while new wheel designs update the rolling stock. Even with its updated appearance, bold the GLS is not, favoring handsome lines that should age better than the wild styling cues of its more trendy competition. Photo 6/14 | A new three-spoke steering wheel and instrument cluster display bring subtle changes to what was already a very user-friendly, luxurious place to spend time. Photo 7/14 | Each of the GLS350d鈥檚 seven passengers are all but guaranteed plenty of space. Even the third row can accommodate adults, as long as they鈥檙e of average size or smaller.

However, the available massaging and fan-ventilated front bucket seats are the best places to spend time in the GLS. Inside, the GLS looks similar to the GL, but an all-new infotainment system, three-spoke steering wheel, and interior colorways betray it as a 鈥?7 model. The center screen adopts the modern, mounted-tablet look, standing out from the dashboard rather than being integrated into it. It鈥檚 a change this author likes very much, but others on the trip criticized the iPad-inspired styling, and admittedly, we wonder how long such a trend will be in style. Will the dash tablet look as dated in 20 years as car phones do today? Behind the wheel, the GLS feels very much like it did when it was called the GL, but that鈥檚 not intended as an insult. It retains its predecessor鈥檚 soothing freeway demeanor, surprisingly sporty handling, and impressive powertrain smoothness. The latter point is most commendable when considering the diesel V-6鈥檚 inherent imbalance and the 9GTRONIC transmission鈥檚 numerous gears, but driving the GLS confirms the engine and transmission operate imperceptibly in almost all driving conditions.

What鈥檚 more, the new automatic transmission鈥檚 extra cogs make keeping the engine-formerly-known-as-Bluetec within its broad powerband even easier. No matter what鈥檚 asked of it, the engine is responsive and entertaining, with good off-the-line power for freeway merges and left turns, while the gearbox鈥檚 adroit downshifts easily dispatch passing maneuvers. Photo 10/14 | The redesigned interior includes a new center screen mounted on top of the dash. The look is modern and trendy, but not everyone loved it. Controlling the screen through the standard COMAND system is easy, as it offers both a scrolling wheel and a touchpad for simple inputs. Also visible are the terrain setting controller and air suspension controls, and both are easy to use. The newly standard Airmatic air suspension is well suited for a variety of driving tasks. Around town and over broken pavement, it soaks up bumps very nicely, with a firm and muted 鈥渢hwomp鈥?announcing the tires鈥?progress.

On the highway, it settles into pleasant smoothness, and its composure befits a vehicle that might occasionally see 100 mph or more on the German Autobahn. Indeed, our freeway speed limits barely scratched the surface of the GLS350d鈥檚 dynamic range, and we enjoyed all-day comfort in each available interior, from base imitation-hide MB Tex to optional leather seating and top-spec designo leather. The GLS350d also had no trouble with any of the impromptu off-roading to which we subjected it. 70,000 SUV to do extreme off-roading, but rest assured: the GLS鈥?4Matic all-wheel drive can easily handle your family vacation to Vail in February, then tow your UTVs to the sand dunes in July. Photo 12/14 | This European-market Mercedes-Benz GLS350d wears AMG-inspired styling that鈥檚 currently only available in the U.S. GLS550. However, if Benz offers it on other versions of the GLS, it would cure a concern some have with the SUV: overly staid styling.