Mercedes-Benz SL [R231] (2016 - 2021) used car review

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By Jonathan Crouch

Introduction

Luxury sports car buyers traditionally sold on the charms on a Mercedes SL will certainly be sold on the much improved version of the MK6 model which sold between 2016 and 2021. They'll like the lithe proportions and deft detailing, the powerful engines and the luxurious technology. More sophistication when it comes to transmission and drive dynamics certainly meant that in this enhanced form, this 'R231'-series design had more to offer. It's a special car. As every SL should be.

Models

2dr Cabriolet (4.0, 6.0 petrol]

History

There aren't many truly iconic cars in the modern motor industry - but this is one of them: the Mercedes SL. This improved version of the MK6 'R231'-series model which had originally launched in 2012 appeared in 2016 and was cleverer and better looking; more than ever before, a very sophisticated kind of sports car.

Significant development of this model line is something that SL buyers are well used to. Over six generations spanning as many decades, everything changed about this car - yet in many ways, nothing was very different. For Three-Pointed Star buyers, it still remained the ultimate expression of sporting opulence and the SL model line remains perhaps the definitive face of this legendary luxury brand. Yet one that over more than sixty five years has changed from supercar to sports roadster and from there through boulevard cruiser to autobahn bruiser. A design, in other words, that through its lifetime, has managed at different times and in different forms to define everything a sportscar should be.

When first the SL appeared in 1952 to spearhead the brand's peacetime return to motorsport, the post-war German economic miracle had hardly begun and many Mercedes factories still lay in ruins. Undaunted, the company's head of testing Rudolph Uhlenhaut decreed that the marque would use this car to win the Le Mans 24 hour race - which it duly did, the perfect platform for the brand's subsequent successful return to the Grand Prix grid. And that might have been the end of the SL story had it not been for an entrepreneurial Austrian-born US businessman called Max Hoffman. Recognising the sales potential for a car like the SL, he persuaded the Mercedes board to reinvent it as a different kind of sporting machine, more of a grand touring GT, still fast, but not as frantic.

So were laid the foundations for this 'R231'-series model. The Gullwing W198 version of the Fifties, the Pagoda W113 model of the Sixties and the R107 series made famous by the Ewings on TV in 'Dallas' in the Seventies. Hi-tech arrived in 1989 with an R129 generation that pioneered pop-up rollbars and integral seatbelts. And more was served up in 2001 with an R230 series design whose folding metal vario roof gave SL buyers both coupe and roadster rolled into one. This replacement 'R231'-series car arrived in 2012 and it properly lives up to its name. 'SL', after all, stands for 'Sport Leicht' and this car, like that one, was made almost entirely from lightweight aluminium. By 2015 though, it was clear that beyond the clever fundamentals, further embellishment was needed. Customers wanted a sleeker look and more dynamic driving aids, plus by now, the engineers had developed a smoother 9-speed auto gearbox to go with the extra media connectivity and more advanced safety features that could be carried over from mainstream models. Hence the need for this significantly revised MK6 SL, launched in the Spring of 2016, the car we're looking at here. It was ultimately replaced by a Mercedes-AMG 'R232'-series model in late 2021.

What You Get

If you know anything at all about this car, you'd recognise one without the badge work, admiring, perhaps, the way that the grille on this 'R231'-series model was positioned to visually lengthen the bonnet. Or the shoulder lines that rise from the headlamps and stretch like tensed muscles along the bodywork into the tail lights.

All of this is as it was in the original version of this 'R231' sixth generation SL. What changed with this revised post-2016 model was the front end, revised to be far more elegant and imposing. Mercedes' legendary 300SL Panamerica racing car provided the inspiration for the facelifted car's more steeply-raked 'diamond'-style radiator grille with its chrome-plated louvre and jewel-like chromed pins. At the wheel, few changes were made over the original version of this sixth generation SL - but then, few were needed. As with other Mercedes models, influences were drawn from the world of aviation, with gorgeous jet-turbine-style air vents dominating a wing-shaped dash with a centre console modelled on the flight deck of an aircraft.

Unlike the close-fitting cockpit you get in an SLC or an AMG GT Mercedes sports car from this period, the cabin offers plenty of space to spread out, thanks to the general increase in size of the MK6 design. Dating the dash slightly is the relatively small 7-inch size of the 'COMMAND Online' colour infotainment screen, along with the fact that the cabin lacks the mouse-style controller you'll find in more recently designed Mercedes models, functionality instead delivered by an old-style swivelling rotary controller alongside the gearstick. Still, at least the 'COMMAND' set-up was standard across the range, offering some classy vehicle parameter displays and fully integrated with the 'Apple CarPlay' system, which will be welcome news for iPhone users.

What You Pay

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What to Look For

Overall, it turns out that this 'R231'-series MK6 SL is one of the more reliable sports cars out there. The issues that do arise tend to be more related to electronic gremlins than the engine. Obviously buy with care - there are a lot of electrical features that could go wrong and you need to make sure that all the powered seat systems work properly and infotainment screen and instrument displays function as they should. Obviously, check the powered roof for water leaks - maybe with a trip to the local car wash. And insist on a fully stamped-up dealer history and inspect the big alloy wheels for scuffs that could require a price reduction. We haven't heard of any issues with the optional 'ABC' 'Active Body Control' suspension system but of course it'll cost a lot to put right if it goes wrong, so you might want to target a car with the standard suspension set-up instead.

There were a number of recalls for this model that you should be aware of. For the rear suspension mounting (models built in April 2019), the passenger door lock (for models built between October 2017 to April 2018) and the passenger airbag (models made between March and November 2018).

Replacement Parts

(approx based on a 2017 S500 Cabriolet - Ex Vat) An air filter is around £51. An oil filter is around £12. Front brake pads sit in the £173 bracket for a set (for rears it's around £215). A tail lamp is around £337-£351.

On the Road

The sixth generation SL was a more sophisticated thing than most of its predecessors thanks to lightweight aluminium underpinnings and in post-2016 facelifted guise, the car got some extra technology that did quite a bit to improve the driving experience. Standard models - namely the 367bhp V6 SL 400 or the 455bhp V8 SL 500 - got a smoother, more efficient 9G-TRONIC PLUS 9-speed automatic gearbox which helped improving running costs that saw the SL 400 managing 36.7mpg on the combined cycle and 175g/km of CO2 (both NEDC figures). This transmission's shift ratios are one of the parameters that can be tweaked via 'DYNAMIC SELECT', a driving modes system that represented the other key addition to this SL's road going repertoire. As with most such set-ups, this one also allows you to alter steering feel, throttle response, stability control thresholds and the settings of the suspension, all to better suit the way you want to drive.

If we were buying, we'd want to look at a model fitted with what was originally a pricey option on standard models, the 'Active Body Control with curve tilting function' package. This gives you active suspension that automatically adapts to your speed and the way you want to drive, plus through the corners, the set-up will proactively lean the car into the bend, reducing body roll and pressing you down into your seat, rollercoaster-style. Even without the tilting technology, an SL is a more involving thing than a rival BMW 6 Series or Maserati GranCabrio from this period would be, thanks to feelsome steering and assured traction aided through the corners by standard torque vectoring. And of course, it'll be very fast in a straight line, especially if you opt for one of the top Mercedes-AMG models, the 5.5-litre V8-powered 585bhp SL 63 or the flagship 6.0-litre V12-engined 630bhp SL 65.

As for the clever vario roof with its electrically-folding metal panels, well that's still something that sets this SL apart from almost every other rival in this segment from this period. Its operation was made more user-friendly in this revised SL, though it remained slightly annoying that, in contrast to rag top rivals, you have to stop before the mechanism will work. Still, you can in this facelifted model make it work at speeds of up to 25mph and the whole process only takes 18s from start to finish. Once all the panels have slotted Swiss army knife-style into place, there's the folding hard-top advantage of greater roof-up refinement than a fabric convertible could provide.

Overall

This is a very special car - and not only because of its status as the first large-scale production Mercedes-Benz to feature an all-aluminium body. Like its predecessors, the sixth generation SL offers a unique, fascinating and in some ways contradictory interpretation of sports car motoring. It's not really tailored for a track, yet it's more than just a very grand GT, a combination that won't suit if your preferences lie at either of these extremes. For many though, this will be the perfect way to reward themselves for a lifetime's endeavour, a car that feels genuinely coupe-like with the roof up and roadster-ready, top-down.

Nothing else in this segment from this period manages that quite as well and nothing else in this segment from this time (outside of a lottery winner's Ferrari California) can offer the security of a hard-top folding roof. As for the changes that created this much improved post-2016 version of the MK6 model, well they're very welcome - and not only because of aesthetic updates that gave this car so much more streetside presence than it had before. The enhanced nine-speed gearbox and the 'DYNAMIC SELECT' driving modes system make a big difference to the driving experience and models that were fitted with the optional 'Active Body Control with curve tilting' system are well worth seeking out if you really want to enjoy everything this car's handling has to offer.

In summary, what we have here is an enduring but very modern take on luxury sports car motoring. And a model that's every inch a classic Mercedes-Benz.