Mercedes-Benz’s V6 diesel engine may be getting on in years, but it provides the GLS350d with sprightly off-the-line acceleration, a satisfyingly flexible delivery and, in combination with a new nine-speed automatic gearbox, effortless cruising properties.
With a new in-line six-cylinder oil-burner under development and planned for introduction in 2016, there has been no effort to extend the output of the decade-old 3.0-litre unit beyond that of the older GL 350 CDI. It also continues to generate the same amount of shove, with 457lb ft of torque available from as little as 1600rpm.
In Comfort mode, the engine is terrifically refined. There is clearly a lot of soundproofing concentrated within the body structure to quell noise, but the muted qualities help to make the GLS terrifically relaxing to drive over longer distances.
Up the tempo by turning the rotary drive mode selector on the centre console to Sport and the engine becomes a little more audible but no less refined. The new gearbox plays a part in improving overall performance and refinement levels by bringing two extra ratios, the tallest of which is a wildly overdriven 0.60:1.
Yet despite providing crisp and silken upshifts, it sometimes proves recalcitrant and less than smooth on downshifts. Traction is never in doubt owing to a standard 4Matic four-wheel drive system. Mercedes-Benz claims a 0-62mph time of 7.8sec. Given that it tips the scales at 2455kg, that’s pretty impressive.
As is the combined cycle consumption, which is improved to a notable 37.2mpg, in the process lowering average CO2 emissions to 199g/km. With a standard 100-litre fuel tank, the theoretical range now extends to almost 900 miles. As before, the towing capacity is put at 3500kg.
The GLS delivers the same calm and reassuring dynamic qualities as the old GL. With ample spring travel and the latest iteration of Mercedes-Benz’s AirMatic air suspension, featuring improved adaptive damping control, it is composed and smooth riding, both around town and out on the open road.
Small bump absorption at low speeds is particularly impressive. It also resists float exceptionally well, remaining encouragingly stable over undulating roads. With an optional Active Curve System that employs hydraulic pumps on the roll bars, it also proves to be exceptionally fleet-footed for a car of such size, remaining uncannily flat and neutral during hard cornering.
All this makes the new Mercedes-Benz an enjoyable drive in all weather conditions. It is easily placed on the road, offers fine visibility and its cabin is tremendously well isolated from uncompromising road surfaces. What the GLS lacks, though, is any real engagement and interaction.
The steering is well weighted and loads up nicely as lateral forces build but fails to deliver the sort of communication and feedback of more sporting SUVs. Although, if you were expecting more interaction you’re likely better off focusing your attention more towards the GLE 350 d Coupé.