HOW fitting it was that the upper-large SUV formerly known as the Mercedes-Benz GL was built in Tuscaloosa, Alabama. The renewed and refocused GLS still comes from the country that brought us cheesy fries and supersize deals, all 5.13 metres long and 1.93m wide, and seating even seven supersized individuals luxuriously inside.

The GLS boasts the same multi-link front and rear suspension, chassis, interior, engines and dimensions as last year’s second-generation GL that was about to blow out a trio of birthday candles. However, the largest Mercedes-Benz SUV now has a political ticket with the S-Class.

A headline mechanical change is the addition of a nine-speed automatic for $116,900 diesel GLS350d (or $135,900 GLS350d Sport) and $135,900 petrol GLS500 models, while the flagship $217,900 Mercedes-AMG GLS63 retains a seven-speed auto.

Those plus on-road costs pricetags not only deliver a lot of metal for the money in relation to a Mercedes-Benz sedan, but also a Range Rover that is $50,000 pricier to start with. Against the similarly priced Range Rover Sport the GLS is simply bigger, with standard (rather than optional) seven seats and properly adult-sized legroom back there.

More expensive, too, is the $140,500 Lexus LX570 that is only a V8 petrol offering. The Audi Q7 starts from $103,100 for a turbo-diesel V6 equivalent to the entry GLS350d but it is smaller and less well equipped.

Every GLS comes standard with newly shaped LED headlights featuring adaptive automatic high-beam that can detect forward or oncoming traffic and only eliminate the portion of light affecting those drivers, leaving a flood of light elsewhere. Likewise adaptive lane-keep assistance can detect freeway lane markings and keep the Mercedes-Benz centred hands-free for 20 seconds at a time – we tried, and it works.

Adaptive cruise control, automatic park assistance with 360-degree camera, blind-spot monitor, air suspension, leather trim with electrically adjustable and heated front seats, and an 830-watt 14-speaker Harman Kardon audio system with new Comand online and Apple CarPlay connectivity, all provide a great mix of safety and standard kit for an entry variant.

Absorb the pricing, specification and competitor set, and it is little wonder Mercedes-Benz Australia expects the GLS to take the baton from the GL and continue to run as the highest selling $100K-plus upper-large SUV in the country.

We saddled into the middle-tier GLS500, expected to be the biggest selling variant in the range, for a brief taster in rural Victoria of the model that Benz admits is little more than a facelift of the GL.

Despite the addition of a new tablet-style 8.0-inch colour screen that adorns many other models in the range, the GLS is starting to feel old inside. The centre console switchgear looks and feels cheap for a vehicle that retails beyond $150K, even one as sizeable as this.

There is still plenty of room, of course, and outboard middle row passengers of the GLS500 also get heated seats to complement the heated/ventilated units up front. The sliding and reclining second row barely affects third-row room either way, and unlike many seven-seaters the boot remains sizeable even with all seatbelts buckled in.

The 4.7-litre twin-turbo petrol engine fires distantly to life, and with 700Nm on board from 1800rpm and nine gears to play with, progress is always sure but smooth in the GLS500. A substantial 335kW of power (up 15kW from GL500) comes in at 5250rpm to help shift 2445kg of upper-large SUV with surprising potency, but also great thirst.

Surely saving $45,000 and purchasing the GLS350d with a 190kW/620Nm 3.0-litre turbo-diesel V6 is the smarter option, given its claimed combined cycle fuel consumption of 7.6 litres per 100 kilometres is far more palatable than the GLS500’s 11.3L/100km. The gap would widen when exercising the latter’s 0-100km/h claim of 5.4 seconds, and if there is no need to, then the claimed 7.8s of the diesel is no deal breaker.

According to its maker, GLS buyers love to tow horse floats, and both 350d and 500 are rated at a maximum 3.5 tonnes.

In terms of steering and suspension, the GLS500 is eerily similar to the GL500 and that is mostly good news.

The previously available Comfort and Sport air suspension modes continue, and each endows this big Benz with wafting ride quality even on 20-inch wheels.

Selecting the cushier setting delivers greater body float, where the firmer mode ties the body down but causes the tyres to nibble over small surface irregularities.

In either case the GLS500 remains a quiet, smooth place to be, and the addition of a new setting marked Individual means the driver can mix-and-match suspension settings with steering weight and drivetrain preferences. Turning response is most impressive in the lightest Comfort mode, but the transmission can be greedy grabbing taller gears in its Eco or Comfort setting, so Sport best keeps it on the boil.

Surprisingly given all that power, but unsurprisingly given the weight, the GLS500 can occasionally feel sluggish low in the rev range and the automatic can be a fraction tardy to respond. Everything about this vehicle’s response is measured and far from sporty, which is probably as it should be.

More time is required behind the wheel of the GLS500, on twisty roads in particular, to see if the standard bodyroll-cancelling active anti-roll bars work a treat.

For now, though, it is safe to say the Mercedes-Benz GLS retains the GL’s status quo. It does not feel new in terms of its dashboard design or weight-saving measures, of which there are approximately none to be seen, and nor does it really feel like an S-Class in any way. The GLS500 appears expensive in relation to the GLS350d as well.

However, as a proper seven-seater with a touch of luxury plus genuinely impressive active safety equipment, wrapped in a quiet and smooth-riding package with enough torque to lug bodies and tow animals, there are good reasons why the GLS is expected to remain number one in its segment.