Mercedes-AMG SL review

In a move harking back to the fourth-generation SL from 1989, it also ditches the two-seat layout and aluminium folding hardtop of its predecessor for a more versatile 2+2 interior and, as the traditionalists have been crying out for for quite some time now, a return to the classic fabric hood brought to the first open-top SL in 1957.

There’s also a big push on the digital front, with an interior and appointments that combine to make those of the previous SL appear very dated indeed. It’s all aimed at giving the SL a truly broad appeal against rivals as diverse as the Aston Martin Vantage Roadster, BMW 8 Series Convertible, Jaguar F-Type Convertible and Porsche 911 Cabriolet.

“When you look back into the history of the SL, you see that it all began with motorsport. With the new model, we’ve attempted to make that link again,” says Jochen Hermann, AMG’s chief technical officer. “But we haven’t forgotten that customers these days also place a high priority on versatility, which is why we’ve made adjustments to the layout to give it two extra seats that make it easier to live with as an everyday car. We were able to start from scratch without building on an existing structure.”

You can judge the design for yourself, but there’s no denying the visual links to the six-year-old GT. This is particularly evident in the traditional cab-backward profile as well as the detailing at the front and at the rear. Both are a big step away from the design of the Mk6 SL, givingthe new car a much more dramatic appearance than its predecessor with clear hints of the original in the shape of its Panamericana front grille and shapely boot line.

It has grown, too: length is up by 88mm at 4705mm, while width and height are increased by 38mm and 44mm respectively at 1915mm and 1359mm. This makes the SL 259mm longer, 24mm narrower and 71mm taller than the two-seat GT.

It’s the wheelbase that has grown the most, though. It’s extended by 117mm over the old SL, at 2700mm, to help accommodate those new rear seats. There are also corresponding increases in the track widths and a drop in ride height, creating a very confident, hunkered-down stance.

The new AMG SL's mechanicals in detail

The new SL is based on its own unique spaceframe structure. Different in design to that used by the GT to accommodate the lengthened wheelbase and fashioned from a combination of aluminium, carbonfibre, magnesium and steel, it is manufactured at Mercedes’ plant in Bremen, northern Germany, where the roadster is assembled beside the Mercedes-Benz C-Class Estate, EQC, GLC and more.

The whole structure is claimed to weigh just 270kg. However, the increase in dimensions, the packaging of the rear seats and other developments such as the inclusion of a four-wheel drive system for the first time, all contribute to a 125kg increase in weight for the initial top-of-the-line SL 63 variant, which tips the scales at 1895kg. The upshot, however, is a claimed 50% increase in rigidity over the already sturdy structure used by the GT.

Underpinning it all is a largely bespoke steel suspension. It uses a new five-link double-wishbone set-up at the front and a multi-link arrangement similar to that of the GT at the rear, in combination with standard adaptive dampers and new lightweight coil springs developed specifically for this application.

SL 63 buyers also get hydraulically operated anti-roll bars as part of a newly developed Active Ride Control package. These are a first for AMG, replacing the conventional mechanical bars of the lesser SL 55. 

Interestingly, Hermann says the switch from the old MRA platform to the new MSA one has allowed Mercedes to position the SL’s axles lower. He claims this brings about a significant lowering in the centre of gravity compared with the old SL.

While a lot is new, the two twin-turbocharged 4.0-litre V8 engines available from the start of UK sales are familiar enough. The M176 unit found in the SL 55 delivers 469bhp and 516lb ft of torque, propelling it from 0-62mph in a claimed 3.9sec and on to a top speed of 183mph. The SL 63 uses the more heavily tuned M177 unit, with 577bhp and 590lb ft, allowing it to dispatch 62mph from standstill in a slightly sharper 3.6sec and reach an impressive 195mph.

As well as an altered intake system, repositioned intercoolers, a new oil pan, changes to its crankcase for added cooling efficiency and a modified exhaust, the latter version of the AMG powerplant benefits from revised active engine mounts. These stiffen and soften according to load, isolating vibrations within the body structure and substantially reducing load change.

Generous engine bay space brought on by the long bonnet has also allowed both V8s to be mounted well behind the front axle for improved weight distribution.

Both models run an AMG MCT Speedshift nine-speed automatic gearbox with a wet clutch and steering wheel-mounted shift paddles. Attached directly to the engine rather than as a transaxle within the rear axle, as on the GT, it’s allied to an electronically controlled rear differential on the SL 63 or as an option as part of the AMG Dynamic Plus Package on the SL 55.

There are five driving modes: Slippery, Comfort, Sport, Sport+ and Individual. A sixth, called Race, is standard on the SL 63 but again an option on the SL 55. There’s also AMG Dynamics, a system that controls the electronic stability control in four settings: Basic, Advanced, Pro and Master.

Other drivetrains are planned, including a petrol-electric plug-in hybrid one similar to that used by the new S580e, although that isn’t expected to figure until the second half of 2022 at the earliest. There’s also talk of an all-electric variant, but Mercedes is remaining tight-lipped on these rumours.

Exploring the AMG SL's interior

One of AMG’s aims with the new SL was to give it a luxurious yet versatile cabin with all the digital technology and connectivity of the flagship Mercedes-Benz S-Class. 

Opening the long door reveals an interior that’s as far removed from the old SL as the newly drawn exterior. The two-seat layout in use since the Mk5 arrived in 2001 has been replaced by a 2+2 configuration, although the rear seats are suitable only for smaller children or as extra storage space.

The low-set front seats are more heavily sculptured than before and have their headrests integrated for added support and a more sporting look, plus Mercedes’ neck-warming Airscarf system.

The leather-bound dashboard is dominated by a 12.3in digital dial display and a 11.9in infotainment touchscreen, which can be tilted from 12deg to 32deg to prevent reflections. It’s all controlled by Mercedes’ MBUX system with conversational voice control. There’s also a flat-bottomed multifunction steering wheel with touch-sensitive controls. And for the first time, a head-up display is available as an option.

It’s suitably high on perceived quality, although some elements could be better thought through. The control mechanism to raise and lower the multi-layered hood, for one, is unnecessarily fiddly.

What's the AMG SL like to drive?

AMG’s V8 is as characterful here as ever. There’s a hearty throb of exhaust blare on start-up and lots of distinctive mechanical engine noise in more sporting driving modes once you get under way. The SL 55 delivers huge flexibility and plenty of pace but, with its extra 108bhp and 74lb ft, the SL 63 is the clear performance leader, offering noticeably sharper in-gear properties and breathtaking acceleration on a wide-open throttle.

The gearbox is slick on upshifts – perhaps not as rapid as you get from rivals’ dual-clutchers but reliably smooth, while the constantly variable four-wheel drive system enables the considerable outputs to be placed on the road with great effect. Traction is greatly enhanced over the old rear-driven SL, as exhibited in the claimed acceleration figures.

There’s an inherently more athletic character to the whole car in line with the aim to make the SL more driver-oriented than it has been in recent generations. You can dig into the deep reserves with great confidence.

The SL 55 recommends itself as the more accomplished everyday proposition with a broad spectrum of ability. However, the SL 63 is always a tick more responsive, faster, louder and, in the end, exciting to drive.

When you dial things back, the SL delivers outstanding cruising qualities. The broad spread of torque offered by the V8 combines superbly with the tall gearing at the upper end of the gearbox to provide wonderful effortlessness from the drivetrain at constant motorway speeds. Both models manage to compress long distances with inherent ease. Don’t expect more than 25mpg, though, even on the most sedate of journeys.

It all comes with a new level of driver engagement. Recent SLs haven’t wanted for straight-line speed, but their dynamic qualities have been compromised to a certain extent by the decision to provide them with a modified platform and underpinnings from other more mainstream Mercedes models.

This new one couldn’t be any more different. It offers great agility, balance, body control and, when you go searching for it by switching the AMG Dynamics system to Master mode, mid-corner adjustability.

This is a heavy car with all the luxury you could wish for, yet it operates with the fluidity of movement and responsiveness to inputs of something much lighter and more spartan. The big increase in body stiffness, lower centre of gravity and networked suspension with four-wheel steering all combine to deliver new-found response, sweetly struck handling and great athleticism.

This isn’t a car to muscle along challenging back roads in the manner of some AMG models. Rather, it’s sensitive enough to be guided by relatively delicate inputs. With all the various driving modes, you can tailor the SL just the way you want it.

The electromechanical steering rack, brilliantly weighted, delivers lots of feel and more enthusiastic self-centring than that of the GT, with which it shares elements.

The balance is terrifically neutral with prodigious grip that remains very dependable as lateral forces increase. We have yet to test the standard suspension, but the hydraulic anti-roll bars do a brilliant job of suppressing body roll. The car changes direction with great eagerness, remaining flat, poised and superbly controlled.

The purchase provided by the 305/30-profile rear tyres is quite something. You can be very exuberant with the throttle yet still remain within the bounds of the remarkably high limits.

There’s fun to be had, though, as the torque-laden delivery does allow you to unsettle the back end in the more liberal of the driving modes, which programme the four-wheel drive system to deliver almost exclusive rear-drive traits, with some provocation. It’s all carefully controlled by the electronics.

The optional carbon-ceramic brakes, meanwhile, are typical in character to those of other AMG models, lacking somewhat in feel until they’re well up to temperature but delivering massive retardation.

What remains in question is the ride, specifically its suitability to UK roads. There’s an underlying firmness to the suspension, even when you put the new SL into its most comfort-oriented settings. It’s certainly a long way from the cosseting roadster we’ve become accustomed to over the years.This isn’t to say that it’s harsh. There’s sufficient compliance and control to allow it to cope with poorer surfaces without excessive fidgeting. But larger transverse expansion joints occasionally defeat the otherwise fast reactions of the dampers, leading to some jarring through the stiff body at times.

Road roar is also noticeable on coarser surfaces, taking the shine off the otherwise impressive refinement.