Normally, stating that a new or updated car is just like its predecessor kind of saps the life out of its 鈥渘ewness.鈥?Take the 2017 Mercedes-Benz GLS450, for example. Its close kinship with last year鈥檚 GL450 may not be exciting, but it is a good thing, as that model represented the ideal intersection of price, performance, and fuel economy in the four-model GL-class lineup. For 2017, that family stays the same aside from a minor name change to GLS-class and subtle cosmetic updates inside and out. Sharing its 362-hp 3.0-liter twin-turbocharged V-6 with the pre-refresh, S-less GL450, the GLS450 again slots into the lineup above the diesel-powered GLS350d and below the high-powered, high-priced, eight-cylinder GLS550 and GLS63 AMG variants. 1650 over a GLS350d, and for that extra scratch you get 107 more horsepower at the expense of a few mpg. GL350 diesel and the GL550, the GLS450 compares favorably. The GL350 BlueTec reached 60 mph in 7.5 seconds and returned 22 mpg, while the GL550 accelerated to 60 mph in 5.4 seconds but delivered a dismal 14 mpg. Aside from their new nine-speed automatic transmission shared with the GLS450, the 鈥?7 GLS350d and GLS550 aren鈥檛 expected to perform much differently.

For its part, the new GLS450 smoked to 60 mph in 5.7 seconds鈥攋ust a tick behind the 550鈥攚hile its observed 18 mpg was much closer to the diesel than to the V-8. Those in slightly less of a hurry could argue a strong case for the diesel, as well. The GLS450鈥檚 new transmission is dubbed 9G-Tronic. Its first seven gears sport shorter ratios than all seven speeds in the old transmission. Compared with a 2015 GL450 we tested last year, the GLS450鈥檚 spicier gearing enabled it to reach 60 mph 0.2 second quicker and post snappier 30-to-50-mph and 50-to-70-mph passing times. Some credit for this specific GLS450鈥檚 extra zip could be attributed to its lack of optional extras, which made it weigh 207 pounds less than that 2015 GL450. A straighter line can be drawn between the new transmission and the GLS450鈥檚 enhanced fuel economy. The two extra gears, both of which are taller than seventh gear in the old transmission, are responsible for nudging the GLS450鈥檚 EPA highway fuel-economy estimate northward by 1 mpg, to 22 mpg.

We saw a bigger improvement, as the 18 mpg our GLS450 notched over a few hundred miles topped the 2015 version by 2 mpg. The only other new feature vying for attention is a touchpad controller for the updated COMAND infotainment display. The touchpad, which operates via finger swipes and taps like a smartphone鈥檚 screen, works as well here as it does in other Benz products. But mostly it presents yet another choice for manipulating the COMAND menus in addition to a knob, steering-wheel controls, and voice commands. All else being pretty much equal to the GL450, it鈥檚 little wonder that this model鈥檚 core competencies carry over. The interior seats up to seven in comfort, and although adults will fit in the third row, those chairs will seem most accommodating to children or teenagers. Air springs are standard, and while this suspension dulls the SUV鈥檚 initial responses鈥攖here is some body roll in corners鈥攊t also makes any road surface feel as if it鈥檚 made of memory foam. And despite the body lean, the GLS posted 0.79 g of cornering grip on our skidpad, which is above average for something 72.8 inches tall and weighing nearly 5400 pounds.

The rest of the big Benz鈥檚 dynamic qualities are to be expected, with the steering tracking well on the highway but otherwise being numb and with slow, vague responses to driver inputs. The brakes earn similar marks; the pedal feels reassuring after you pass through a brief squishy zone at the top of its travel, but the GLS450鈥檚 186-foot stop from 70 mph is merely okay for this class. Really, though, the only dynamics that matter are the GLS450鈥檚 highway manners. We took it on a half-day trip from Ann Arbor to the west side of Michigan and back, and the most grueling part of the journey was the sunburn we got at the beach. Fill the GLS450 with people, cargo (up to 94 cubic feet with the second- and third-row seats folded), or both and you can schlep them far and wide in soft-riding quietude. It鈥檚 particularly telling that this fairly sparsely optioned GLS450 seemed so luxurious and relaxing to drive. 3830 Premium package that brought SiriusXM satellite radio, Apple CarPlay, a proximity key, lane-keeping assist, ambient interior lighting, and a power passenger seat. 80,000 is slightly richer than a base, four-wheel-drive Cadillac Escalade鈥攁 rig that鈥檚 closer to the GLS450 in size and general SUV-ness than the more carlike Audi Q7 and Volvo XC90. The body-on-frame Escalade also happens to be slower, worse to drive, less fuel-efficient, and less roomy for people and cargo, which sets up an opportunity for the GLS450.