2017 Mercedes Benz S400d LWB first drive review

The self-proclaimed “best car in the world” - with the modest aspiration of being “the best car of all time” - is back to fight off all-new model challenges from Audi and BMW.

Mercedes-Benz’s latest S-Class is more about increased comfort and safety than handling and performance, despite engines offering more power. The S-Class is Mercedes’ benchmark so it contains the full breadth of Mercedes engineering talent and looks set to assume its traditional ranking among luxury sedans.

What is it?

Mid-model update brings a gentle facelift, though Mercedes says there are 6500 new components – with variants of three innovative and impressive new in-line six and V8 engines – plus a host of semi-autonomous driving abilities.

Why are we testing it?

With the new Audi A8 and BMW 7-Series fighting for the same territory, has Mercedes done enough to keep the S-class at the pinnacle? Does the return to in-line six engines bring a significant step in refinement with that promise of V8 performance and six-cylinder economy?

Main rivals

BMW 7-Series, Audi A8, Jaguar XJ, Lexus LS

The Wheels verdict

The new S-Class does take another step down the road of turning drivers into passengers at a comfort level that rivals the more exclusive Rolls-Royce. The Mercedes, especially in long wheelbase form, serves up an unmatched sense of wellbeing that is almost overwhelming whether at the wheel or in the comfort of its vast rear seat compartment.

Plus refinement of new diesel engine, performance and economy combination, plush comfort, calm personality

Minus occasionally slow to kickdown, new cruise control might irk traditional owners, impression of width never goes away

The Wheels Review

The freshly face-lifted version of the classic German luxury sedan doesn't go on sale until December in Australia. When it does, it will be offered with six separate engines scattered across a range of models: S350d; S400d LWB; S450; S560; S560 LWB; AMG S63 LWB, and the S650 Maybach - the only V12 variant to survive a cull of models at the very top end of the sedan range. Such is the complexity of the range and options that Mercedes claims no two S-Classes built will be identical.

Underneath the familiar exterior – now refreshed by a prominent chrome grille, modified bumpers, and LED headlights and taillights graphics - is a subtly updated version of the previous S-Class’ MRA platform that is shared with the smaller C- and E-Classes, with unique S-Class structural components at the rear. All in conjunction with the standard Air Body Control air suspension, however unlike the three-chamber system unveiled in the latest E-Class, the S-Class maintains the simpler single chamber set-up of the old model. Inevitably, the S-Class’ electrical architecture has been significantly upgraded, and predictably it now supports the widest range of driver assistance system of any Mercedes.

Wheels drove a variety of engines at the international launch, but with the circa-$250,000 400d LWB – boasting a wheelbase of 3165mm versus 3035mm for the standard ‘short’ bodied version - expected to be the local best seller, we concentrated on this new 2.9-litre straight-six diesel that replaces the old 3.0-litre V6. Worth noting, again, that all S-Class models sold in Australia are rear-wheel drive, as the 4Matic of the test car being limited to left-hand drive setups (at least until the next-generation model).

The new twin-turbo in-line six-cylinder diesel delivers 250kW (up 10 percent) between 3600-4400rpm, and a mighty 700Nm across a range from 1200-3200rpm. It features a stepped bowl combustion process, multi-channel exhaust gas recirculation system and, for the first time, variable valve-lift control.

As significant as the performance and economy figures are (0-100km/h in 5.2sec, 5.2L/100km consumption through the combined cycle), it’s the new engine’s refinement and smoothness that really impresses. In this respect, it’s a huge step over the old V6. From the wheel, the engine is barely audible at idle, it revs quickly while power delivery is virtually linear, changing up at 4500-4600rpm under full throttle, somewhat shy of the 5250rpm redline. It even sounds good.

The new 9G-Tronic gearbox works with a 2.47 final drive - seventh, eighth, and ninth are overdrives – to have the engine wafting along at around 1200rpm at Australia’s 110km/h speed limit, the driver oblivious to the gear changes along the way. Despite the twin-turbo set up, there is the merest hint of lag at very low rpm before the engine is in the peak-grunt zone of instant response.

The diesel lacks the 48-volt electric motor assistance of the also impressive 2.9-litre in-line six 320kW petrol-powered S500, yet speed builds quickly and there is just a distant hum from the engine. With double-glazing standard on Australian cars, the cabin feels utterly isolated from the plebeian dramas of the outside world.

You don’t buy an S-class for driver involvement. This is a big, especially wide and heavy car, that’s utterly at home on the Autobahn: the master of long distance travel at speeds that are only legal in Germany. In Comfort mode, where the car’s character is all about the exceptional ride comfort, there’s a hint of float and even roll. Selecting Sport provides an instant cure for its composure, with only a marginal impact on ride comfort, though the driver is always aware of its weight when diving into tight corners. The creamy steering is a little vague and light at low speeds in Comfort, but it seamlessly builds effort if you toggle to a sportier setting that adds more precision.

The cruise control feature in the new 2018 S-Class goes a step beyond the functionality of the new E-Class. It is now able to automatically adjust its speed for curves, intersections, changes in speed limits, and toll gates, based on its GPS data. The result is a system that allows the driver to use cruise control—and even its steering-assist function—much more often on secondary roads and not just on motorways.

The S-Class’ cruise control is perhaps the biggest advance in the technology since adaptive cruise allowed drivers to use the feature in heavy traffic. Initially, it’s harder to trust than simple adaptive cruise control system. With the car in its default Comfort mode, the cruise control will noticeably slow the car for corners—more so than you might on your own—before quickly accelerating back to the set speed.

In Sport it doesn’t slow as much and carries more momentum through bends. It also responds to speed limit signs, though occasionally the system disregarded the signs and failed to speed up.

Learning to trust the car to slow on its own when approaching intersections is more disconcerting because the driver must be ready to brake for oncoming traffic at a roundabout or to brake at a stop sign. If there’s no oncoming traffic and no braking is required, the driver can stay off the brakes and let the car do it all; if you do need to brake, the driver needs to hit the resume button to reactivate cruise control. Active Lane Changing Assist lets the driver change lanes with a flick of the turn signal; the car checks the road ahead and the traffic behind to make sure the coast is clear, before oozing itself across the road.

All this technology was impossible to operate on Mercedes’ old, and excellent, single wand cruise control. Because of that, all cruise functions are relocated to the left spoke of the steering wheel where some familiarisation is needed. Long term S-Class buyer-owners, who’ve become accustomed to the old wand won’t be pleased.

Inside, the front seats offer tremendous comfort over longer journeys. The cabin styling has been subtly refined, with higher-grade materials within the dashboard, which remains dominated by two high definition displays, now under a single glass pane, for the instruments and infotainment system. In the rear, the long wheelbase provides exceptional leg room and comfort, as demanded for cars at this end of the luxury car spectrum.

With a clear choice of models, and performance up to the AMG S63 (0-100km/h in 3.5sec), this latest version sets out to meld graceful speed and ultimate comfort with cutting edge technology. Nobody does it better than Mercedes.

Specs

Model: S400d LWB
Engine: 2925cc six-cyl in-line, dohc, 24v, diesel, turbo
Max power: 250kW @ 3600-4400rpm
Max torque: 700Nm @ 1200-3200rpm
Transmission: 9-spd automatic
Weight: 1950kg
0-100km/h: 5.4sec
Economy: 5.2L/100km combined
Price: $250,000 (est)
On sale: December