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The most powerful diesel engine ever fitted to a G-Class raises the game for Mercedes' iconic SUV

What is it?

You’re looking at the sensible version of an extrovert car.

Sensible because it is the entry-level model with the best fuel economy; extrovert because this is still a G-Class (née Wagon), and is therefore an archaic presence on any road it graces. It is more capable off it than almost anyone would ever need, too, and hugely expensive. When it goes on sale in January, the G350d tested here costs nearly £100,000, which is at the upper end of most rivals’ ranges.

But consider the specification and slowly that price begins to make sense. We’ve already driven the rejuvenated G-Class in flag-flying, snorting AMG guise, but some things bear repeating. Mercedes spent many years over-hauling its hand–assembled icon. It has enlisted the expertise of AMG for the suspension design and gave its engineers and designers sleepless nights in the attempt to preserve the general feel of the original (Land Rover take note). As a result, the car betters its old self not only in terms of breakover and approach angles etc, but also in terms of usability. And is recognisably G-Class.

To that end, the changes have been targeted. Rumour has it in excess of €5 million was spent getting the bonnet-mounted indicators – four decades out of date – to adhere to modern safety regulations and yet recirculating-ball steering has given way to a rack-and-pinion set-up that is laser-guided by comparison. Likewise, the click-snap door handles haven’t gone anywhere, and neither has the chromed cover for the spare wheel – both are carried over unchanged – but the front suspension is now by double wishbones for more precise steering control and greater ride quality. The G-Class also continues uses a ladder-frame chassis, and yet the interior finishing is truly superb (its general topography, of course, has changed very little). 

What’s new here is Mercedes’ OM656 straight-six – the most powerful diesel engine ever fitted to a G-Class. It forms one third of an engine line-up that otherwise consists of twin-turbocharged petrol V8s (though, as it stands, in the UK we’ll have the 586bhp G63 but not the 416bhp G500), and also serves in the luxury Mercedes-Benz S-Class.

In Mercedes’ flagship saloon there are two states of tune, and it's the lower one the G350d gets, with 282bhp from 3400rpm and 442lb ft arriving at only 1200rpm. Admittedly, these are relatively modest gains over the 3.0-litre BlueTEC V6 diesel that powered the outgoing G350d, but a combined fuel economy of 29.4mpg is a useful improvement over the old car’s 25.2mpg. The claimed 0-62mph time has also fallen from 9.1sec to just 7.4sec, which looks to be a similarly useful real-world improvement. 

2 Mercedes g 350d 2018 fd snow side

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What's it like?

You’ll struggle to find any mode of transport more drenched in personality than the AMG-fettled G63. And yet, while the G350d isn’t as entertaining, it is without question the more likeable sibling. This is largely because diesel power reinstates a touch of utilitarian charm and honesty to the experience of driving a G-Class. You might be no more inclined to use the car to anything like its full terrain-conquering potential, but with the diesel the possibility of such a workout does somehow seem more probable.

And even if you don’t, there are more tangible benefits: our test car returned 32mpg along a flat stretch of autobahn between Innsbruck and Munich. Given the new G-Class weighs the thick end of 2.5 tonnes and still has the aerodynamic qualities of a parachute, that’s pretty good going. Mercedes pioneered in passenger cars the use of stepped-bowl pistons with its latest range of four-cylinder diesel engines, and the same propagation-enhancing technology is found within the OM656. In Eco – along with Comfort and Dynamic, one of the car’s three powertrain modes – the engine will also decouple from the lazily smooth nine-speed gearbox to coast at idling speeds for as long as you refrain from touching the brake or throttle pedals.

What's more, this new straight six is refined not only by the standards of those few machines with three locking differentials and a rigid rear axle, but by those of any segment. It first delivers all that torque with a wide, bass-heavy warble that quickly smooths out and remains smooth as silk through to 5000rpm. I’d say that sound is a bit more present from within the cabin of the G-Class than an Mercedes-Benz E-Class, though without a microphone you wouldn’t know for sure. That shows just how far this off-roader has come. Six hours in the saddle doesn’t precipitate the kind of aural fatigue you got in the old car – a feat all the more impressive given Mercedes has reclined the rake of the windscreen by only a single degree. Don't expect the same isolation from wind noise you'd get in a BMW X5, mind.

And, really, the G350d of 2018 still isn’t overtly cultured. This is especially true without the AMG-tuned suspension of the G63. Mercedes’ improvements to the car’s ride and handling are vast, but bumps in the road can still send a well-defined ripple through the chassis. At times it’s as though each suspension turret is two-foot taller than it actually is. Corner with any commitment and it’s all the suspension can do to stop the bodywork first collapsing over the hard-worked outside front tyre, then its counterpart over the rear. The G-Class is still very much a car with a high and peripatetic centre of gravity. On most roads a Range Rover Sport would feel like an Alpine A110 by comparison, and the driving position feels conspicuously perched (great off-road; less so on it).

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Should I buy one?

The G-Class and Porsche’s Porsche 911 share a common theme: the most accessible model in the range is by far the most authentic. Porsche’s seminal sports car was conceived as a more delicate device than the ludicrously well equipped, fat-wheeled, wide-body spaceships of today and the G-Class originated as a military vehicle. The supercar power and low-profile tyres of the G63 are a fun sideshow but for many prospective owners it simply won’t be a sustainable relationship. After a few miles it’s all too tiring and, frankly, too superficial.

By contrast, the diesel engine in the G350d raises the G-Glass’s game. A relatively frugal but strong and quiet performer, it complements the car’s opulent interior and newfound capability as a cruiser. With the chassis and cabin improvements, it means that for the first time in a 40-year existence, the G-Class is something normal people, doing normal things, could happily live with. Just about. And, of course, you still get almost unparalleled off-road ability.

You might still be brave to look past the similarly expensive but more sophisticated, comfortable likes of a Range Rover Autobiography, but no longer would you be stupid. Maybe the G-Wagen's gone soft.

Mercedes-Benz G-Class G350d specification

Where Hochgurgl, Austria Price £94,000 On sale January, 2019 Engine In-line 6 cyls, 2925cc, turbocharged diesel Power 282bhp at 3400-4600rpm Torque 443lb ft at 1200-3200rpm Gearbox 9-spd auto Kerb weight tbc Top speed 124mph 0-62mph 7.4sec Fuel economy 29.4mpg (combined) CO2 253g/km Rivals Range Rover Autobiography SDV8, Bentley Bentagya Diesel

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Richard Lane

Richard Lane
Title: Deputy road test editor

Richard joined Autocar in 2017, arriving from Evo magazine, and is typically found either behind a keyboard or steering wheel.

As deputy road test editor he delivers in-depth road tests, performance benchmarking and supercar lap-times, plus feature-length comparison stories between rival cars. He can also be found on Autocar's YouTube channel

Mostly interested in how cars feel on the road – the sensations and emotions they can evoke – Richard drives around 150 newly launched makes and models every year, and focuses mainly on the more driver-orientated products, as is tradition at Autocar. His job is then to put the reader firmly in the driver's seat. 

Away from work, but remaining on the subject of cars, Richard owns an eight-valve Integrale, loves watching sportscar racing, and holds a post-grad in transport engineering. 

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Comments
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madmac 19 December 2018

For the best offroad vehicle

For the best offroad vehicle this has no equal,for the best sports car the 911 has no equal.For the best combination for a family needing or wanting these things is this and a 911T-perhaps modified by Litchfield! On Scottish moors in the winter with the family and never get stuck like a modern SUV would with no low range box,and tearing around the narrow roads in the T ! perfect! For the less well off,the new Suzuki and a base Caterham! Each to his/her own budget.

xxxx 19 December 2018

Best off road vehicle?

Emmm not sure if a 2.5 tonne, £100k vehicle with over 2 feet of LCD sceen to go wrong is the best thing to go off roading in the outback/Africa. I'd go for the Toyota Land Cruiser,

si73 19 December 2018

xxxx wrote:

xxxx wrote:

Emmm not sure if a 2.5 tonne, £100k vehicle with over 2 feet of LCD sceen to go wrong is the best thing to go off roading in the outback/Africa. I'd go for the Toyota Land Cruiser,

 

Thats alright, he was going to the Scottish moors.

289 19 December 2018

@xxxx

Err, I doubt many will end up in the outback xxxx.

Scottish Baronial estates, UAE deserts etc....oh and for the AMG 6'3's - most essentially to take advantage of the off-road ability....the Kings road to Knightsbridge.

mafearon 19 December 2018

Price

This car is worth exactly what people will pay, the same for all vehicles. 

if it cant sell at £94+ then there will be discounts. No different than any other car that is priced too high for the market to sell at. 

Personally, if I could justify paying for this, I would. I was lucky enough to drive an armoured version around several testing courses. 

Herald 19 December 2018

Quite like it, but ...

 .. at anything up to 60-65k, I get this vehicle: at 94 I struggle. For that sort of money the temptation must be to opt for a less compromised on-road experience, and if I did need its undoubted off-road functionality I'd have to question the necessity of this degree of luxury and expense. Falls between two stools in my opinion, but some of the well-heeled will no doubt ensure Mercedes shift a few.