Key considerations
• Available for £14,000 (really!)
• 3.5-litre NA V6 or 3.0-litre twin-turbo V6, rear-wheel drive
• Basic SL 350 is more than quick enough in the real world
• Nicely understated and mechanically strong
• Maybe not as ‘special’ as some previous SLs
• … but still a comfortable, classy and cheap two-seat tourer
Today’s buying guide is on the Mercedes-Benz R231 SL two-seater sports that was on sale between 2012 and 2020. The R231 is only the sixth-generation SL, amazing really when you consider that it’s been in Mercedes brochures since the early 1950s.
Now, as a powerfully built PH type you might be expecting us to concentrate on the 4.7 V8-powered SL500 or the twin-turbo 5.5 SL 63 AMG. Fine machines to be sure, but actually we’re going to focus on what we reckon is the unsung hero of the R231 range, the entry-level SL 350 that launched in 2012, or the SL 400 as it became in 2014.
Why? Well, for a start, an SL of any stripe, ‘basic’ or range-topper, is going to be a highly desirable motor. SLs have traditionally set the standard in a corner of the market that we might, in a moment of verbal diarrhoea, call relaxed open-topped sporting luxury. Then there’s the performance, which in truth is less relaxed than you might think. The 350’s maximum power of 302hp might seem a bit measly on the page, but when it’s combined with a nice spread of torque, a smooth 7-speed transmission and a new aluminium body with magnesium roof frames that trimmed 140kg off the R230’s weight, it’s surprising how smartly you’ll be moving down the road in one of these. Even the entry-level SL 350 is a five-second 0-62mph car.
The final reason for zoning in on the 350? The prices that you’ll pay for this generous package of performance, luxury and heritage. We saw a 115,000-mile 350 with no mention of any damage repairs at two quid under £14,000. That was exceptionally cheap and would obviously need closer investigation, but even if we ignore that one there’s no shortage of 350s on the used market from £16,000, which seems like excellent value for a car that was over £72,000 new in 2012.
In mid-2013 the SL 350 and 500 became available with fancier AMG Sport trim, a clever electric glass sunroof, bigger brakes and Park Assist. A year later the SL 350 was superseded at the bottom of the SL range by the SL400 which was powered by a smaller (3.0 litre) but twin-IHI-turbocharged V6 offering 328hp and 354lb ft. Despite carrying an extra 50kg or so, the new SL 400 was 0.7sec quicker over the 0-62mph run and not much less economical. Another refresh in spring 2016 powered the 3.0 turbo engine up to 362hp and brought a nine-speed 9G-Tronic gearbox, new safety gear, 18-inch wheels and Apple CarPlay.
Turns out that the R231 we’re looking at here was the last iteration of the classic SL because the new for 2021 R232 SL was shuffled across into the AMG fold. Maybe it was our ham-fisted use of the overwrought M-B UK website (wouldn’t be the first time) but we couldn’t find any of these AMG SLs for sale anywhere in the UK dealership network at the time of writing (September 2022), so in a way you could say that the R231 remains the current model SL, in the UK at least.
Fourteen, or even sixteen, grand for a current model Mercedes SL with a superb drivetrain and a packed specification? That’s bonkers, isn’t it? What’s the catch? You tell us. Oh, we’re supposed to be telling you aren’t we. All right, let’s try and find out if there are any reasons why you shouldn’t be living your best SL-Class life at used C-Class prices. Hurrah for depreciation!
SPECIFICATION | MERCEDES-BENZ SL 350/400 (2012-14/2014-16/2016-20)
Engine: 3,498cc/2,996cc turbo V6 24v petrol
Transmission: 7-speed automatic (9-speed after 2016), rear-wheel drive
Power (hp): 302@6,500rpm/328@5,250-6,000rpm
Torque (lb ft): 273@3,500-5,250rpm/354@1,600-4,000rpm
0-62mph (secs): 5.9/5.2
Top speed (mph): 155
Weight (kg): 1,685/1,730
MPG (official combined): 41.5/38.7
CO2 (g/km): 159/172
Wheels (in): 17
Tyres: 255/45
On sale: 2012-2014 / 2014-2020
Price new: £72,495 (SL 350)
Price now: from £14,000
Note for reference: car weight and power data are hard to pin down with absolute certainty. For consistency, we use the same source for all our guides. We hope the data we use is right more often than it’s wrong. Our advice is to treat it as relative rather than definitive.
ENGINE & GEARBOX
When there’s a V8 to be had in any car range there’s a tendency to ignore any ‘lesser’ six-cylinder engines that might be sitting in the shadows. That’s always been a mistakenly short-sighted view when it comes to Mercedes, whose track record of delivering silky sixes has historically been second to none.
The R231’s first non-turbo 3.5 litre M276 V6 was a lovely piece of kit, refined to the core and perfectly suited to a life of cruising. With direct injection came the potential for carbon build-up, but the M276 was quite resistant to it. Generically, high-pressure fuel pumps can give trouble on DI engines, but the HPFP fitted to the SL wasn’t particularly known for failing, and if it did go it would usually do so gradually over months rather than suddenly, and generally not below 80,000 miles. The symptoms were longer cranking times, hesitation, rough idling and power loss.
The official mpg figure for the SL 350 was over 40mpg and regular returns in the mid-30s were perfectly attainable. Overall the M276 has been a reliable and strong unit in both 3.5 NA and 3.0 turbo iterations. It was timed by chain. Some pre-2014 engines did suffer from tensioner issues causing rattling, check engine lights and fault codes, but M-B put out improved parts after that date. Many of the weak tensioners were replaced under warranty so with luck it should be safe to buy early cars.
Both the seven- and nine-speed transmissions fitted to the SL 350/400 were smooth and efficient. Paddle operation wasn’t lightning-fast but only low-speed downshifts were vaguely noticeable. There was a problem with some 7-speed boxes locking themselves in Park, the fix for which was nothing short of a new gear selector. The paperwork may show it’s been replaced, or that there’s no sign of any replacement. Either way, life going forward should be sweet.
SL servicing was straightforward enough, operating on a 12-month/10k alternation between major and minor. It wasn’t as dear as you might have feared either, minors at the official dealer coming in at under £300. Two-yearly majors are somewhat more, obviously. If you were having the plugs changed (it was advisable to do that every four years to minimise the chance of them seizing in the heads) and having fresh gearbox oil and brake fluid put in, the cost could drift into four figures. Knocking one or two of those items off the worklist might get the bill down to under £500 if you’re lucky. Non-dealer specialists would typically charge two-thirds of the dealer’s quote.
Dying spark plugs and coils are more or less a normal part of modern motoring. Non-turbo engines tend not to burn through their ignition components as quickly as turbocharged ones, which was another tick for the 3.5 NA engine. Timing was by chain rather than belt, so no worries there.
CHASSIS
As mentioned earlier, the R231’s aluminium/magnesium body chopped a hefty 140kg off the previous SL’s weight and boosted rigidity by 20 per cent, but most of it not all of that weight saving was put back on in the form of new safety systems and ‘toys’, so there wasn’t much difference between the handling of new and old SLs. Having said that, the R231 felt lighter on its feet than the 1.7-tonne weight suggested, and the braking was very good. The response of the variable-ratio electromechanical steering was improved on the R231, and it felt great at lower speeds, but the sense of detachment at higher speeds confirmed that the SL was still more boulevardier than bolide.
When looking at cars to buy, don’t get carried away into thinking that you have to have big wheels on an SL. All they’ll do is add an unwanted sharp edge to the ride quality. Be comfortable in your own skin and resist the temptation to go large. If you feel you really need a knobbly ride, an SL with the AMG Sports package gives you a lowered ride height courtesy of stiffer springs.
Compared to the preceding gen-five R230, the R231 had wider tracks and more aluminium in its multi-link all-round suspension componentry. It also had torque vectoring and adaptive damping. The two modes were Comfort and Sport. New SL buyers could specify the ‘Magic Body Control’ version of Benz’s long-developed Active Body Control, an electronically controlled hydropneumatic suspension system which packaged up ride height adjustment and self-levelling with the suppression of body roll. On later models there was the option of ‘Active Curve Tilt’ that positively leant the car into corners, motorcycle-style. ABC gave you a best of both worlds mix of pliant ride with minimal roll but used buyers might think that the high cost of repairing it when it goes wrong makes it a less desirable thing to find on an SL.
A very small number of SLs were recalled in early 2017 to rectify a fault that could lead to power steering failure. Another recall was issued on April 2019-built cars for a rear suspension problem. Odd cars have been brought into dealerships for the replacement of front suspension arms that had a bush issue.
BODYWORK
Any convertible you’re thinking of buying needs a good powerhosing to make sure it doesn’t let the water in, and the R231’s Vario roof was no exception. Folding metal roofs generally have an inglorious reputation, and the Merc was not immune to jamming – engaging the latches for the roof/boot space divider could be difficult – but problems like that were much less common on the SL than they were on other roof-folders. Deploying it was a 20-second operation that could only be carried out on the pre-2016 SL when it was stationary. On cars built after that you could operate it at speeds of up to 25mph without having to fiddle with the divider.
The extras list included ‘Magic Sky Control’ in the panoramic glass roof, an £1,800 option using electro-reactive particles to give you the instant ability to switch from transparent to opaque, a lovely touch. Another piece of ‘magic’ naming that was perhaps not as grown-up sounding as a typical SL owner might like was ‘Magic Vision Control’. This was a wiper system which fed heated screenwash water through holes in the wiper blades to minimise any interruption to your visibility, and which operated differently according to the season and whether the roof was up or down, but it was a cute and effective gizmo. A reversing camera was a cost option.
INTERIOR
Every SL came with widely adjustable heated leather seats, digital radio, satnav, parking sensors and dual-zone climate control – pretty much all you need for an easy life.
The quality of the R231’s interior was superior to its predecessors, but you might think there’s some similarity between the R231’s switchgear and knobbery and that of lesser Benzes of the same era. You’d be right there because a lot of it is shared with those common or garden cars. That’s OK though because in the SL it was all sitting in a beautifully assembled environment of high-quality leather, metal and glass, while you as the human were luxuriating in a space that was airy in every dimension: height, width and depth. In fact, it was the most spacious car in the class for front-seat passengers. No car seat is ever going to be perfect for everyone, but the seats in an R231 got closer to it than most. Visibility was excellent.
The sacrifice for all that front-compartment room was no room for rear seats, but let’s be honest, what would you rather have, lots of room all the time or less room all the time to allow for an eventuality that might never happen? Exactly. The SL design also allowed for the provision of a lockable box behind the passenger seat, another really useful feature.
There was good space under the composite bootlid too, even when the roof was folded away. Hands Free Access for opening the boot by a foot wave was a neat option. The boot reflected the SL’s suitability for two-up touring, holding a decent 364 litres of cargo even when the roof was in the down position. That was 129 litres up on the previous SL and enough for two golf bags. Space rose to around 500 litres with the roof up.
Top-down driving was at least as refined and comfortable as top-up, especially with the optional Airscarf neck heater and electronic wind deflector that most new buyers specced. Life was even better if you had the Bang & Olufsen stereo option, although the standard setup was excellent thanks to a clever ‘Frontbass’ design which moved the front bass speakers from the doors to special structures in the footwells to create resonance chambers. A batch of 2014 SLs built-in spring 2014 were recalled for faulty airbags.
PH VERDICT
Comfortable, classy and cheap. You don’t often see those three adjectives together in a car review, but they surely apply to the R231 Mercedes SL. It’s easy to forget just what a standard-bearer the SL has been over such a long period in the world of two-seater sports cars, and the R321 was a noticeable improvement over the R230 in terms of quality.
A Porsche 911 Cabriolet would be one open-air rival for an SL350/400, and it would be a sharper driving car with nominal rear seats, but try finding one of them at the mid-teens money that will snag one of these Mercs. Otherwise it’s a 6 Series BMW or Maserati Gran Cabrio from the period. Neither of those would provide a superior driving experience.
Prices at the cheap end of the R231 market are heavily mileage dependent. As noted in the Overview you can find a 2012 115,000-mile 350 at £14k, but next door to it in the classifieds you might well see a 50,000-mile car from the same year for £19k. The most affordable example on PH classifieds at the time of writing was this 45,000-mile SL 350 from 2013 with the AMG Sport upgrades that came in that year and the panoramic glass sunroof. It’s cheap at £17,494 because it’s Cat S repaired. For £1,500 more there’s this fully serviced pre-AMG 2013 car with the desirable Airscarf fitted, plus Active Park Assist which does the steering for you.
The cheapest 328hp SL 400 was this 58,000-mile 2015 car in white with red leather at £25,995. You could bag a 362hp 9-speed 400 for under £30k in the shape of this 80,000 mile 2018 car. Throw another £2k into the pot and you’ll be able to halve that mileage in this 2016 car.
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