Mercedes-Benz GT63 vs Mercedes-Benz SL63

What's the difference?

The Mercedes-AMG GT 63 S 4-Door Coupe fulfils the brief for an ultra-fast, ultra-luxurious, four-door weapon. The theatre that surrounds it will be enough for some, and those that want to a have a serious crack won’t be disappointed.

The new Mercedes-AMG SL63 4Matic+ is guaranteed to turn heads for decades to come. But there’s enormous design and engineering substance underpinning this car’s undoubted good looks. Stunning performance, superb dynamics and top-shelf safety make this a powerhouse GT to be reckoned with.

Note: CarsGuide attended this event as a guest of the manufacturer, with accommodation and meals provided.

At a fraction over 5.0 metres long and just under 1.9 metres wide, the GT 4-Door Coupe is substantial, but an overall height under 1.5 metres sets up an aggressive stance that screams speed.

Fat guards are filled by dark 21-inch rims, and the low-set, bulging bonnet sits behind menacingly angular ‘Multi-beam’ LED headlights sitting either side of AMG’s now signature ‘Panamericana’ grille, looking ready to chew up and spit out lesser machines.

It has to be said that calling this car a four-door is a bit cheeky because technically it’s a hatch, and to my eyes at least the gentle rearward slope of the turret and large cargo door enhances the design’s understated power.

Inside is a sea of top-shelf nappa leather, with the twin-widescreen cockpit layout (two 12.3-inch hi-res displays) dominating the dash. Carbon-fibre is applied liberally (in the 63 S), and the grippy sports steering wheels and seats look and feel close to track grade.

Turbine-style air vents (four in the centre, and one at each edge) are now a Mercedes design signature (used in the back as well) and they combine with the brushed metal finishes around the broad centre console and on the pedals to deliver a sense of occasion and anticipation just sitting in the car. Fit and finish is flawless.

Rather than a strict two-seater, this time around the SL adds the flexibility of ‘+2’ rear seating while the previous 'Vario’ folding hardtop has been binned, the new car returning to a traditional, electrically-folding and weight-saving (-21kg) soft top. 

Mercedes-Benz design chief Gorden Wagener started the new model’s development from a ‘clean sheet’ and Mercedes-AMG says “not a single component comes from the predecessor SL, or any other model such as the AMG GT Roadsters”. 

Always a subjective call, but I think this car’s proportions are just about perfect. The lengthy bonnet with its twin longitudinal ‘Power Domes’, raked windscreen and fat haunches create a wide stance and presence that’s almost impossible to ignore.

Aggression, as with the sinister headlights and 21-inch rims, is subtly combined with soft curves along the flanks and around the rear. Note the seamless door handles.

And it’s not all about aesthetics. Active aero has been integrated into the front apron and retractable rear spoiler. Plus the ‘Z-fold’ roof design does away with the need for a separate cover.

The interior is sub-zero cool with slick screens, an 11.9-inch display covering multimedia and a 12.3-inch unit for instrumentation ahead of the driver, being particular highlights.

Turbine-style air-vents at the leading edge of the split-level dash and alloy trim elements are a tip-of-the-hat to SLs past and the deft mix of large flat surfaces with complex curves oozes design confidence.

At surface level the GT 4-Door Coupe is a more liveable alternative to the GT Coupe, for blazing fast road trips, and obscenely rapid grocery runs. But the fact is it’s sooo much more practical than its two-door stablemate.

Space in the front is generous with storage running to twin cupholders in the centre console, as well as a modest glove box, decent sized door bins (with room for bottles), and a lidded storage box between the seats.

Connectivity and power options include 12-volt outlets, multiple USB ports and NFC (Near Field Communication) tech for easy Bluetooth and Wi-Fi connection of enabled devices.

Rear seat room is healthy. At 183cm I was able to sir behind the driver’s seat set to my position with plenty of leg and headroom to spare. Although anyone travelling in the rear centre position will have drawn the short straw, because the back seat is sculpted with bolstered positions for the two outer positions only.

A fold-down centre armrest offers more storage with a lidded box and a pair of cupholders and twin vents in the rear of the front centre console can be adjusted individually as part of the four-zone climate control system.

Hit the button, near the driver or on the key fob, to open the tailgate door and you’re presented with 461 litres (VDA) of cargo space, with the rear seat split-folding 40/20/40 to increase flexibility and liberate considerably more room.

There are tie-down hooks at each corner of the boot floor, an elasticised cargo net is included, and 12-volt power is provided.

Don’t bother looking for a spare wheel, the tyres are run-flats, and both GT 4-Door Coupe models are a towing no-go zone.

In the context of a high-performance GT, practicality is pretty impressive.

At just over 4.7m long the SL is a sizeable machine and much of its lengthy (2700mm) wheelbase is devoted to making the driver and front passenger comfortable.

There’s plenty of space for that pairing and just enough storage to cope with the ‘things’ they’ll typically bring with them.

Door pockets offer enough room for a few odds and ends, although you’ll struggle with even a medium-size bottle unless you’re willing to lay it down horizontally along the top of the aperture.

A handy lidded bin between the front seats doubles as a centre armrest, there are two cupholders under a sliding lid in the centre console and the glove box is a decent size. 

Power and connectivity options run to four USB-C ports, a 12-volt socket and the wireless device charging pad.

Then there are the rear ‘+2’ seats, and Mercedes makes no bones about the fact they’re intended for occasional use only, even suggesting a 1.5m occupant height limit.

And there’s no doubt they offer a handy emergency seat or a fun kids’ zone. Just ask a Porsche 911 Carrera owner how much this kind of seating arrangement increases a sports car’s flexibility.

At 183cm I gave the back seat a crack, which meant sliding the front (passenger) seat way forward with the backrest close to upright. But I squeezed in, and there was just enough legroom for a person in front at the same time. 

With the roof in place there’s the added pleasure of cranking your head over to around 45 degrees. But it’s do-able! 

No storage, adjustable ventilation, or power back there. But that’s fair enough, especially given there are USBs available in the front centre storage box.

Boot volume is 240 litres with the roof up and 213 litres with it folded, which is enough for some light luggage, and not too shabby when you think a Toyota Corolla hatch offers up just 217 litres (with all seats up).

There’s a 12V socket in there, but don’t bother looking for a spare, in the event of a flat your only option is a repair/inflator kit.

Priced at $373,370, before on-road costs, the new SL63 4Matic+ will be battling top-shelf performance soft tops including (in ascending dollar order) BMW’s M850i xDrive Convertible ($307,100), the Porsche 911 Carrera GTS Cabriolet ($386,900) and even exotics like the Lamborghini Huracan RWD Evo Spyder ($422,606). 

Value for money is a relative concept in this part of the market, although equipment highlights include a head-up display (with augmented reality nav), 11-speaker, 650-watt Burmester surround sound audio, ambient lighting (choice of 64 colours), hectares of Nappa leather trim, dual-zone climate control, an 11.9-inch central multimedia screen (running Merc’s latest ‘MBUX’ software), 12.3-inch configurable digital instrument display and 21-inch forged alloy rims.

There’s also the ‘Digital Light System’ built around three high-power LEDs in each headlight, refracted and directed through 1.3 million ‘micro-mirrors’ to create a combined resolution of 2.6 million pixels.

The ‘Neck Scarf’ function is added to the top of the front seats to keep your neck and the back of your head warm as the temperature drops, the heated, ventilated and massaging front seats feature eight-way electric adjustment and three memories, there’s a heated steering wheel, Android Auto and Apple CarPlay connectivity, wireless device charging and more.

Worth noting the big 21-inch rims in a ‘10-twin-spoke’ design are standard issue with an alternate ‘multi-spoke’ pattern available as a no-cost option. 

But if all that’s not enough you can opt for ‘AMG Performance seats’ ($2490) which grip you even more securely but delete the massage function.

Or there’s the ‘AMG Night Package’ ($6990) which adds wheels in matt black (with “high-sheen finish rim flange”), darkened head- and tail-lights, an aero package, black badging, black radiator fins and interior trim elements in black chrome.

Then you can go the whole hog with the ‘AMG Carbon Fibre Package’ ($11,990) which brings the wheels in matt black, exterior carbon elements, carbon mirrors, carbon interior trim and a steering wheel in a combination carbon-fibre and Dinamica (synthetic microsuede).

The V8 volcano generating this car’s prodigious power is the same all-alloy, direct-injected, 90-degree 4.0-litre (M178) unit used in the two-door GT coupe, in this case with dry rather than wet sump lubrication.

Its two turbos are located in the engine’s ‘hot vee’ to improve under-bonnet packaging and reduce the distance exhaust gas has to travel to reach each twin-scroll turbo, and that charged air has to travel to the cylinders (minimising throttle lag).

Maximum power of 470kW is available between 5500-6500rpm and peak torque of no less than 900Nm is delivered across a broad plateau from 2500-4500rpm.

The GT 53’s 3.0-litre in-line six-cylinder unit produces 320kW at 6100rpm and 520Nm from 1800-5800rpm, with an ‘EQ Boost’ starter-alternator unit between the engine and transmission adding an extra 16kW/250Nm.

Drive goes to all four wheels via a nine-speed automatic transmission, in the 63 S featuring a wet, multi-disc start-off clutch, and a conventional torque converter in the 53.

The ‘4Matic’ all-wheel drive system sends drive to the rear axle permanently, and the front wheels variably, with the torque split continuously adjusted according to conditions and driver input.

This new ‘4Matic’ all-wheel-drive SL63 features AMG’s (M177) 4.0-litre twin-turbo V8, superseding the previous rear-wheel-drive SL’s similarly configured 5.5-litre unit.

Hand built by one AMG technician from start to finish, it produces 430kW (around 580hp) from 5500-6500rpm and 800Nm across a broad plateau from 2500-5000rpm.

It’s something of a mechanical masterpiece, and the previous seven-speed auto transmission, driving the rear wheels only, has been replaced by a nine-speed dual-clutch auto (with wet multi-disc start-off clutch) sending drive to all four wheels via Merc’s ‘4Matic’ AWD system.

At the time of writing, Mercedes-Benz Australia hadn’t issued Australian Standard combined cycle fuel economy figures for the GT 4-Door Coupe, but NEDC Euro standard numbers are 9.4L/100km for the GT 53 and 11.3L/100km for the GT 63 S. NEDC CO2 emissions for the combined cycle are 215g/km and 257g/km respectively.

Despite the GT 63 S’s stop-start system (with glide mode) and eight- to four-cylinder deactivation tech (available from 1000-3250rpm), over close to 280km of mainly open road driving on the launch program we saw a dash-indicated figure of exactly 16.0L/100km.

Minimum fuel requirement for both models is 98 RON premium unleaded, and you’ll need 80 litres of it to fill the tank.

Mercedes-AMG’s official fuel economy number for the SL63 on the combined (WLTP) cycle is 13.9L/100km, the 4.0-litre twin-turbo V8 emitting 319g/km of CO2 in the process.

On the roughly 300km launch program we covered urban, B-road and some freeway running, returning an (indicated) average of 17.5L/100km. And that reflects some enthusiastic driving along the way.

The fuel tank requires 70 litres of 98 RON premium unleaded to fill it which translates to a theoretical range of around 500km, dropping to 400km using our real-world number.

Okay, so first up this is one fierce four-door, claimed to sprint from 0-100km/h in 3.2 seconds, which is properly supercar fast, and if you’re game and have a driveway long enough, able to blast up to a maximum velocity of 315km/h. Wow.

And behind the wheel it feels every bit of it. A flat-chat, launch-control assisted take-off narrowing your field of vision ever-so slightly and inducing an involuntary tensing of the abdomen.

The accompanying soundtrack is suitably ferocious, with a full-noise pass delivering a satisfyingly sharp spike on the decibel meter.

With 900Nm available from just 2500rpm there’s always an ocean of torque available, and by the time you’re into the upper rev range in anything above third gear you’re either headed for licence loss or the first corner of your favourite race circuit.

The nine-speed ‘MCT’ transmission in the 63 S features a (wet) take-off clutch and the big four-door puts its power down beautifully, the rear axle LSD and carefully tuned ‘4Matic’ all-wheel drive system seamlessly distributing torque between the axles and individual wheels able to make best use of it.

Slip into manual mode and the fun factor dials up a few notches with sharp and positive moves between ratios. But if you prefer leaving it in drive the transmission will sense what you’re up to and pick up ratios at just the right spot to keep things on the boil.

The electrically assisted steering delivers good road feel and the 63 S’s rear axle steering helps with precise and predictable turn-in on cornering.

The adaptive damping system helps keep this roughly 2.0-tonne weapon in check on twisting backroads, the optimal setting for our launch drive being engine, transmission, steering and exhaust turned up to 11, with the suspension in ‘Comfort’ mode. Spot-on.

A monster brake package comprises big ventilated discs (390mm fr / 360mm rr) with six-piston fixed calipers at the front and single-piston floating units at the rear. They wash off speed quickly and calmly time after time.

But dial things back to a less aggressive, more everyday mode and the ride comfort remains a stand-out trait. Even on big 21-inch rims the GT 63 S turns coarse-chip rural bitumen into a smooth carpet, with very little noise filtering into the cabin.

The front seats are super-supportive and comfortable for long stints behind the wheel and ergonomics are top-shelf with all major controls ideally placed and easy to use.

And if you want to get into the nitty gritty the AMG ‘Track Pace’ function in the Comand media system captures and analyses over 80 vehicle-specific data points as well as circuit lap times. Fun

I recall driving the AMG SL65 around the backroads of Tassie a few years ago and that twin-turbo V12 monster famously packed 1000Nm of torque, while this car ‘only’ has 800.

But there comes a point where enough is enough… and this is enough!

With maximum torque available from 2500-5000rpm and peak power (430kW) on call from 5500-6500rpm there’s always stupendous acceleration available with a squeeze of your right foot.

Claimed 0-100km/h time is supercar fast at 3.6 seconds, while top speed is a toupe-troubling 315 km/h. And that’s electronically limited!

A typically ferocious engine noise and howling exhaust note accompany rapid progress and shifts from the nine-speed dual-clutch transmission are quick and positive, not to mention especially enjoyable using the steering wheel-mounted paddles.

There are six ‘AMG Dynamic Select’ drive programs from Comfort through to Race, the latter including a Drift Mode, which we didn’t experiment with. Nor did we dip into the ‘AMG Track Pace’ system for circuit-focused mapping and timing

However, far from drifting, the grippy Michelin Pilot Sport 4S rubber (275/35 fr - 305/30 rr) plants the car securely with the all-wheel-drive system and electronic locking rear diff playing their part.

I found the perfect set-up was in the ‘Individual’ mode with the engine, transmission and steering in racier settings and the suspension in ‘Comfort’. The adaptive damping in this configuration mixes smooth ride compliance with sharp dynamic response.

The car’s aluminium space frame chassis is part of a body structure mixing aluminium, magnesium, fibre composites and various strength steels.

Torsional rigidity is claimed to have been improved by 18 per cent and despite the lack of a roof the SL feels tight and solid.

Suspension is by alloy double wishbones front and rear with adaptive damping and active hydraulic anti-roll stabilisation standard (so, no physical anti-roll bars).

At the same time the 4Matic AWD system is able to vary torque distribution up to 100 per cent to the front or rear axle depending on where drive can be put to best use.

The speed sensitive, variable ratio, electronically controlled steering is accurate and turns in beautifully with good road feel. No doubt assisted by electric rear steering able to adjust the angle of the rear tyres by up to 2.5 degrees.

All this adds up to a hugely impressive package that, despite its 1970kg kerb weight, feels agile, athletic and able to attack corners like an overgrown hot hatch, putting its power down with unwavering authority.   

While indecently fast the SL63 can also stop rapidly with the AMG high-performance braking system standard. 

Huge composite ventilated and cross-drilled discs (390mm fr - 360mm rr) are clamped by six-piston fixed alloy calipers at the front and single-piston units at the rear. They wash off speed calmly and consistently with perfect pedal feel.

Even at highway speeds, particularly with the windows up, normal conversation is easy with the roof down. But if you need to raise (or lower) it, the operation takes 15 seconds and is possible up to 60km/h. 

Under the heading of miscellaneous observations, the turning circle is a not insubstantial 12.8m, so beware in the car park.

A front axle lift function is a welcome standard feature, raising the car’s nose 30mm with the press of a button. And lift locations are stored in GPS data, so the car will subsequently remember to lift itself at the same place, even if you don’t! 

Heating and cooling for the front seats combined with the heated steering wheel and Air Scarf neck warming makes winter top-down driving a pleasure.

The digital instrument display is not only crystal clear, it can be changed through multiple configurations, including a tunnel-like graphic for engine revs as well as specific readouts for speed, g-force, the lot.

At the same time, the central media screen’s angle can be adjusted to better cope with reflections and the windscreen wiper system Merc calls ‘Magic Vision Control’ channels fluid along the wiper arms onto the rubbers, which isn’t new, but works spectacularly well here.  

No independent ANCAP safety assessment at this stage but the SL63 is fitted with the ‘Driving Assistance Package Plus’ which includes a heap of active (crash-avoidance) tech including AEB (with pedestrian detection), active cruise control, lane keeping assist, lane change assist, traffic sign assist, ‘Active Traffic-assist’ and ‘Active Steering Assist’. 

There’s also tyre pressure monitoring and the ‘Active Parking Assist with Parktronic’ self-parking system supported by a 360-degree camera view and multiple sensors. 

If a crash is unavoidable the airbag count runs to eight, including side bags for rear occupants. There are ISOFIX anchor points for child seats or baby capsules in the two rear and front passenger seat positions. And an active bonnet is designed to reduce injuries in the case of a pedestrian impact.

Mercedes-Benz covers its AMG range with a three year/unlimited km warranty, like the other two members of the German ‘Big Three’ (Audi and BMW) lagging the mainstream market where the majority of players are now at five years/unlimited km, with some at seven years.

On the upside, Mercedes-Benz Road Care assistance is included in the deal for three years.

Service is scheduled for 12 months/20,000km (whichever comes first) with pricing available on an ‘Up-front’ or ‘Pay-as-you-go’ basis.

For the GT 63 S pre-payment delivers a $1230 saving with the first three services set at a total of $6450, compared to $7150 PAYG. Fourth and fifth services are also available for pre-purchase.

The SL63 4Matic+ will be covered by Mercedes-AMG’s five-year/unlimited km warranty, with roadside and accident assistance included for the duration, both of which are expected in this category. 

Maintenance intervals are 12 months/20,000km, and a fixed-price service plan lists an average of $1583 for each of the first three visits to the workshop. Not exactly small change, but not unheard of in this part of the market.