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AMG-developed roadster packs a serious punch, with its twin-turbocharged eight-cylinder engine

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The Mercedes-AMG SL 55 is the entry point to the eight-cylinder variants of the Mercedes-AMG SL.

Its message is clear – with a revised raison d'être. The SL is going Porsche 911 hunting, and it has variety to help it.

The SL is now a proper AMG-only package.

There are three V8-engined variants (with the Mercedes-AMG SL 63 being a PHEV) and a four-cylinder model with the motor made famous by the A45 AMG super-hatch. Each on sits in an all-new chassis, as the SL moves into more sporting territory than it previously occupied.

Prices for the SL 55 start from around at £150,000, which gives this AMG plenty of competition, not only from Porsche but also Maserati and, at a push, Aston Martin. How well does it stack up? Let's find out.

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DESIGN & STYLING

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Mercedes-AMG-SL-55-4MATIC-rear-corner-richard-lane

For an idea of how different the R323-generation SL is to its predecessor, consider the press pack, which runs to nearly 20,000 words.

A dissertation-length work, it contains an onslaught of information that explains Mercedes’ repositioning of the model from aristocratic two-seat tourer with sporting undertones to something much more muscular, aggressive and, according to at least one exec, with the basic ingredients to tempt people out of their 911 Cabriolets and Targas. Long story short, the SL has been properly AMG-ified.

The SL has been overhauled and has a new game plan.

It starts with an all-new aluminium platform. The material used isn’t surprising, given the SL has since 2011 been constructed from lightweight aluminium, but this time the structure is dramatically more rigid (the old R231 was hardly a damp flannel either) and the development has been undertaken not at Sindelfingen but by AMG in Affalterbach.

That last fact alone is quite the statement of intent from Mercedes, and the Mk2 Mercedes-AMG GT coupé has already inherited plenty of this new SL's hardware.

The long-snounted roadster now comes with front driveshafts and rear-axle steering, for added performance and agility, and returns to having a lighter fabric (rather than a metal folding) roof. Lastly, and for the first in a very long time, there are back seats.

INTERIOR

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The new SL’s cloth hood may be the first difference you notice, but this is the first SL in several generations to offer second-row seating – although you certainly wouldn’t call it a proper four-seater.

Mercedes advises that those back seats are “for passengers up to 1.5 metres tall”. They have very upright backrests and aren’t easy to access or exit, even for passengers who meet that height restriction. But while the ‘+2’ seating erodes the cabin’s sense of exclusivity, they do add some practicality – even when only carrying shopping bags.

I and many others would prefer a few more physical controls.

You dip low to berth the driver’s seat but will find it comfortable and widely adjustable. There is electric adjustment in just about every direction, but while much of that is automated, it’s not always done so intelligently. Open the door to get out and the seat will motor back and recline automatically to ease your egress, for example. But it will do so even when the sensors for the rear seatbelts tell the car that the chair behind is occupied – and where there was likely to have been scant leg room to begin with.

The head restraints, too, have a habit of lowering themselves automatically as the hood folds up and back – but they don’t then return to their previous positions.

The hood itself is an impressive piece of design, folding and stowing quickly and quietly into a surprisingly tight space that leaves a reasonable amount of luggage room. Some testers bemoaned the route by which it is controlled, however – not by a knurled physical switch but by a dedicated screen on the car’s portrait-oriented central infotainment display. Lowering the roof in a car such as this ought to be a bit of theatre to look forward to, but here it’s a disappointingly fiddly process via a surface that, when the roof has been down, can become a bit too warm to hold a fingertip against comfortably for the required 15 seconds.

The SL’s tilting infotainment display is the central focus of a reductionist cabin design of a theme that Mercedes has dubbed ‘hyperanalogue’: the combination, supposedly, of a simplified classic-looking fascia geometry with the latest digital infotainment technology. But the sense of built-in quality around that screen, and of any really lavish sense of inherent expensiveness and heft to the cabin overall, is a little underwhelming.

It’s all pleasant enough, but there is rather too much plastic masquerading as aluminium in evidence here, along with fewer physical controls with which to engender any substantial expensive tactile feel in the first place, to put this car on a level with the most luxurious-feeling convertibles. 

ENGINES & PERFORMANCE

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Few engines are more recognisable either from behind the wheel or from the pavement than AMG’s monster M177 4.0-litre V8, which has been in service for many years but for the SL gains new intake and exhaust plumbing as well as a specific oil pan.

In the SL 55 specifically, it makes a relatively tame-sounding 469bhp, with a robust 516lb ft of torque. In this day, these are not the most exciting figures, true, but if that’s what you want, the 195mph SL 63 will be your thing. There the same V8 is boosted to 577bhp and 590lb ft. 

The driving modes make a big difference and are customisable too.

Still, the SL 55 has enough torque to be getting on with, and rather than outright top-end power, it is the easy-going sledgehammer manner of this beefcake mill that informs much of the car's personality, with the 516lb ft delivered from only 2000rpm. It never feels less than emphatic.  

It means that while SL 55 lacks truly jaw-dropping performance, it is ready to shift itself at almost any speed and in any gear. This engine is decently free of lag, too, so the performance really is press-and-go, especially if you've sharpened the throttle-respone by choosing a fruitier driving mode. 

The gearbox is AMG's nine-speed automatic, which is excellent company when you just want to get from A to B and just good enough when you want to enjoy yourself. It doesn't have the dexterity of Porsche's PDK, or even the ZF torque-converter in the BMW M4, but it's smooth and well calibrated. 

RIDE & HANDLING

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Unsurprisingly, such effortless pace plays nicely into the SL 55's GT credentials, which are in general excellent, but for the ever so slight brittleness that creeps into the ride quality on poor surfaces.

Perhaps the SL 63 - with its McLaren-esque, anti-roll-bar-less, cross-linked hydraulic damping system – will do better in this respect, but the SL 55, on traditional semi-active suspension, is hardly what you would call rustic. With a comfortable, plush, cosseting cabin and free-breathing vertical body control, most of time it just gobbles up big miles without thought. 

The SL 55 charms you superficially with its thumping engine and easy pace.

It eats up B-roads with less natural ease but plenty of enthusiasm nonetheless. Traction is superb, to the extent that this chassis will take full power and torque in second gear on a cold, greasy surface. The agility-enhancing effects of the rear-wheel steering, which works in contrary motion to the front wheels at anything below 60mph, are also apparent and impressively fluent. This is an easy car to place at speed and it gives you the confidence to chase the throttle and revel in that monster V8.

As a luxury, cross-country, all-season GT of surprising precision, the SL 55 works well. And there are, of course, many, many chassis and engine modes that give the car pretty staggering breadth. But as a proper 911 rival? I’m not so sure. 

At almost 1900kg, the SL 55 is too heavy, and while clever in the way it manages its mass, the car can never escape its effects. You, the driver, are always aware of it, waiting for it to tug the nose off line through an unexpectedly tight corner, or for the body to fall a step behind what the road is doing. That neither of these things ever really happens is a mark of just how well sorted the SL 55 is, but the point is that you feel as though they might, and that's not so enjoyable.

The electromechanical steering is also somewhat soulless compared with the electrohydraulic set-up in the AMG GT and the four-wheel-drive chassis can be a touch too neutral at times, although perhaps this is one of the car’s virtues. It depends what you're after. If material plushness and dynamic solidity are your priorites, you'll enjoy the Mercedes and love using it. 

VERDICT

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So the new SL 55 is complete and versatile. So much so that you might wonder whether it's trying to do too much. Fast and agreeable to live with the car might be but the GT-leaning driving experience lacks bite and never really gets under your skin, or at least it didn't in an afternoon or two of driving on some of the UK's best roads.

In this sphere, the 911 therefore remains our go-to. There's plenty to like in this ever-so-quick, ever-so-quick rendition of the SL but less, perhaps, to love.

Great car. Great engine. But not as recommendable as a Porsche.

 

Richard Lane

Richard Lane, Autocar
Title: Deputy road test editor

Richard joined Autocar in 2017 and like all road testers is typically found either behind a keyboard or steering wheel (or, these days, a yoke).

As deputy road test editor he delivers in-depth road tests and performance benchmarking, plus feature-length comparison stories between rival cars. He can also be found presenting 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. His job is then to put the reader firmly in the driver's seat.