Petrol vs Diesel: True king-of-the hill Mercedes-Benz GLS crowned

The Mercedes-Benz GLS has had a bit of a checked upbringing since its reveal as the biggest SUV with a three-pointed star 18 years ago.

Mercedes-Benz hierarchy

Once tipped to replace the G-Class, only for Benz to change their minds following a backlash from G-Wagen enthusiasts, a name change mid-way through the second generation’s lifecycle saw the original GL moniker being dropped in favour of GLS.

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Like the M-Class that now went by the GLE moniker, the renaming formed part of a model rationalising aligning Stuttgart’s SUVs with its sedans.

As such, the GLS became the SUV version of the S-Class, while the GLE represented the equivalent of the E-Class.

Straightforward choice

Officially known as GLS since the current X167 generation debuted in 2019, the emergence of a mid-life facelift in April last year had Mercedes-Benz take its time as the South African market launch happened almost exactly 12 months later.

While availed in ultra-luxurious Maybach GLS 600 guise, the surprise absentee was the AMG GLS 63.

As such, the local market, except for the Maybach, offers a straightforward choice between petrol or diesel, both with new names; the GLS 450d that replaces the 400d, and the GLS 580 that usurps the 450.

While experiencing a particular model’s different options only occurs during the launch, an opportunity to sample both the 450d and 580 presented itself less than a month apart.

In a segment still skewed towards diesel, the initial arrival of the 580 came as a big surprise as expectations pointed to the 450d being the first to face scrutiny.

Imposing, yet discreet

Sans the AMG Line aesthetic, the GLS remains an imposing thing to look at as, apart from measuring 5.2 metres, its proportions emit a typical “large-and-charge” persona only rivalled by its arguably is closest rival, the BMW X7 and even the S-Class.

The recipient of a new grille with four as opposed to the two previous horizontal louvres, the refresh further includes a new front bumper with a gloss black finish on the new air vents, a new front under guard protection plate and lightly restyled LED taillight clusters.

Unsurprisingly, the main differences involved the colours and wheels. Whereas the GLS 450d adopts a more sinister look as per its Obsidian Black paint finish, plus the optional R16 800 Night Package, the GLS 580 appears almost restrained in its Selenite Grey hue.

Overturning this though are the optional 23-inch AMG wheels priced at an eye-watering R49 000 versus the 450d’s more sedate, standard, 21-inch alloys.

The refresh hasn’t resulted in the GLS standing out in the same way as the BMW X7, or indeed even the Volvo XC90.

However, and in confirmation of the saying, size ultimately wins and while likely to be viewed as nothing but a pumped-up GLE, the discreet makeover still works in its favour.

Step-in to opulent largeness

Tugging open the door reveals an interior identical to the pre-facelift GLS as the dual 12.3-inch digital instrument cluster and MBUX infotainment system have both been kept, along with the four turbine-style air vents and pair of grab handles on either side of the touchpad on the centre console.

The only significant change involves the latest MBUX software and a new steering wheel, whose attractive design sadly remains blighted by the touch-sensitive buttons that replace the previous physical switchgear.

An annoyance the GLS could have done without, the rest of the interior is an inviting place to be, though some of the materials, especially the optional open-pore anthracite wood applique on both models, felt plasticky and not worth the extra R7 800.

Still not the most intuitive to use, the irksome touchpad can be eschewed for the screen itself, which proved a lot easier and simpler, though still requiring some familiarisation as a result of a number of sub-menus and settings.

In addition to the seat comfort, standard with heating and ventilation, another key point of the refresh involved making more optional features standard.

As such, the expanded ambient lighting package, wireless smartphone charger, 360-degree surround-view camera system, the Multibeam adaptive LED headlights, excellent Burmester sound system and quad-zone climate control are included from the start.

As standard, the GLS’ seven-seat layout involves the second and third rows being electrically retractable using the panel integrated into the boot walls.

While conducted faster manually, getting into the third row requires some careful contorting as the layout of the second row involves the seats moving and then lifting forward rather than tumbling.

An additional caveat related to this is space. While the second row can be configured electrically and specified with heating for an additional R6 600 as the 450d was, space in the third row varies from suitable for children, to small adults in the case of the second being moved more forward than usual.

While this sees a variation in legroom, which won’t lead to any complaints in the second row in “regular form”, headroom remains plentiful and comfort in the second row is unmatched to the point of feeling similar to sitting in an S-Class.

As for practicality, the GLS offers 355 litres of boot space with all seven seats up, which increases to 1 470 litres in five-seat form. With the second row also down, capacity tops out at a van-rivalling 2 400-litres.

Petrol vs diesel

Unsurprisingly, the main split in personality between the pair involves the choice of engines – an area where the big displacement petrol doesn’t live up to the hype.

While powered by the AMG-developed 4.0-litre bi-turbo V8 with 48-volt mild-hybrid assistance, for use in the 580, and not to step on the AMG GLS 63’s toes, Mercedes-Benz has retuned it for smoothness rather than typical AMG brute force.

With 380kW/730Nm on tap, 20kW/30Nm more than before, the V8 still emits a pleasing low-down rumble, but while quick off the mark, runs out of puff quickly and at times, feels delayed in response with the knock-off effect of feeling underpowered.

Admittedly a heavyweight at 2 640 kg, the GLS 580 has a limited top speed of 250 km/h and will get from 0-100 km/h in a claimed 4.9 seconds, though it feels its mass despite the 48-volt EQ Boost system adding 16kW/250Nm for short spells.

In stark contrast, the also mild-hybrid assisted 3.0-litre straight-six diesel in the GLS 450d appears outgunned on paper with only 270 kW of power.

The key though is its 750 Nm of torque which, even without the EQ Boost’s extra 15kW/200Nm, transforms the GLS from a disappointment into a stunner.

Swopping the V8’s bark for a pleasant burble that becomes a relentless growl, the GLS 450d feels stronger and much more responsive, even with the Dynamic Select mode selector switched to Comfort.

In Dynamic, it becomes explosive and while a 20 Nm uptake appears minor, the characteristic nose lift under heavy acceleration is more prominent and the low-down pull unremitting – this despite its 6.1 second 0-100 km/h sprint time and 250 km/h top speed.

Small can be good

Mated to both engines, the 9G Tronic transmission goes about its business in a slick and obtrusive manner, yet while the Airmatic air suspension features on both, it doesn’t translate to a similar ride quality as the same-same shift quality of the transmission.

Possibly as a result of the different wheel sizes, the ride in the GLS 580 felt overly floaty and prone to an unnerving skittish sensation with each surface change.

Quiet and with a weighted feel to the steering, the combination of the suspension and smaller wheels had the opposite effect on the GLS 450d.

Besides feeling more composed and more refined, body-roll was not as extensive.

Although unlikely to matter much to prospective buyers of either model, fuel consumption figures came to a best of 13 L/100 km for the 580 and 9.6 L/100 km for the 450d.

Conclusion

As accomplished as it has become over each of its three generations, the Mercedes-Benz GLS still finds itself tricky position despite its S-Class of SUVs description.

Besides its price, which worked out to R2 954 199 for the 580 and R2 623 637 for the 450d – inclusive of the R77 500 and R209 400 worth of options fitted – the GLS’ closeness to the S-Class remains in what can be seen as either deliberate or a coincidental.  

A strategic masterstroke in the case of the former based on buyer preference of either a sedan or SUV for roughly the same price, the downside involves the GLS offering little to the S-Class overall.

Apart from the usual day-to-day, seldom use will be made of its off-road prowess, or even specified with the revised Off-Road Engineering package.

As such, the smart money remains on the S-Class, never mind the smaller but also cheaper GLE that can be had with seven seats.

The GLS therefore rates as an all-out “want” buy unmatched by any other Mercedes-Benz model, regardless of it being an S-Class or G-Class.

In this regard, the 450d trounces the 580 for being the seven-seat SUV with a three-pointed star you will ever need.

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