BMW 528i vs Mercedes-Benz SL63

What's the difference?

Sleek and attractive in the city,  engaging on a country back road and with plenty of clever technology, the 5 Series sedan ticks all the right boxes as an executive express. If you can stomach the price hike, the six-cylinder 540i is our pick of the bunch.

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.

Hardly a revolution, the 5 Series has instead undergone a few nips and tucks. But if it ain't broke and all that. It might not be the most head-turning offering, but the 5 Series sedan remains sleek, powerful and understated, and it is undeniably handsome on the road.

Its 8mm wider, 28mm longer and 2mm taller than the car it replaces, but it's also around 95kg lighter, thanks to its aluminium doors and boot and a clever magnesium frame for the instrument panel that saved another two kilograms. There's some other clever design elements, too. The kidney grille has active air flaps that open when extra cooling is required, closing when it isn't, reducing drag and helping accleration.

Inside, the 5 Series offers a beautifully crafted yet joyously understated cabin, with quality materials joining modern technology in a seamless way.

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.

This is a full-size sedan, and every seat feels spacious and airy. The sloping, slightly coupe-style roofline does cut into headroom in the back, but human-sized people will have little trouble, even sitting behind a tall driver.

Each trim offers two cupholders in the front, with another two housed in a pull-down divider that seperates the rear seat. And there's two ISOFIX attachment points, one in each window seat in the back. 

The 5 Series' boot opens to rival a surprisingly sizeable storage space, offering 530 litres with the 40:20:40 rear seats in place.

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 hunt for efficiency sees all but the most expensive 5 Series models equipped with four-cylinder engines, including the entry-level 520d, which is fitted with a 2.0-litre diesel unit that will produce 140kW at 4,000rpm and 400Nm from 1,750rpm. That's enough to push the cheapest 5 Series to 100km/h in a not particularly inspiring 7.5 seconds, topping out at 235km/h.

The cheapest petrol, the 530i, arrives with a turbocharged 2.0-litre engine good for 185kW at 5,200rpm and 350Nm from 1,450rpm. That will see you clip 100km/h in 6.2 seconds and push on to a limited top speed of 250km/h.

The turbocharged six-cylinder feels right at home in a car this size, with acceleration effortless and freeway overtaking manoeuvres an absolute breeze.

The 530d introduces the first six-cylinder engine, a 3.0-litre unit that will produce 195kW at 4,000rpm and an impressive 620Nm from 2,000rpm. That's enough to knock off the sprint in in 5.7 seconds and offers a top speed limited to 250km/h.

Finally, the top-spec petrol, the 540i, will produce 250kW at 5,500rpm and 450Nm from 1,380rpm from its 3.0-litre turbocharged straight-six engine. Those are healthy numbers, and enough to welcome 100km/h in a sprightly 5.1 seconds before topping out a limited 250km/h.

Every model is paired with an eight-speed torque converter automatic transmission.

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.

BMW quotes a combined 4.3 litres per hundred kilometres from the 520d, which will also spit out 114g per kilometre of C02. The 530d lifts that number to 4.7 litres per hundred kilometres (which seems a small price to pay for all that extra torque), with C02 pegged at 124g per kilometre. Both diesels get a slightly smaller tank, at 66 litres.

The 530i will sip a claimed/combined 5.8 litres per hundred kilometres, with C02 emissions a claimed 132g per kilometre, while the big 540i requires 6.7 litres per hundred kilometres, with C02 pegged at 154g per kilometre. Both petrol models get a 68-litre tank and require 95RON fuel.

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.

BMW's pre-drive briefing was so technology focused we half expected the black turtle neck and dad jean-wearing ghost of Steve Jobs to emerge from behind a curtain clutching an iPad. Only a minuscule portion was dedicated to the cars' drivetrains, with BMW instead hammering home autonomy functions, technology upgrades and the fact that its car was a preview to "the future".

But once we'd slipped behind the wheel of the all-new 5 Series, it all started to make more sense. Having briefly sampled three models (the 530i, 530d and 540i), we can safely report there's nothing particularly revolutionary about their on-road behaviour. That's not necessarily a bad thing - they do everything you could ask of a car in this bracket. They're mostly smooth and always quiet, the new chassis has done nothing to dampen engagement when you start to ask a little more of it, and it's generally a luxurious experience. But then so was the old car.

But what's new is the technology poured into the 5 Series. Every car gets what BMW is calling its personal co-pilot, for example, which is a set of tricky systems (there's six cameras, five radar sensors and 12 ultrasonic sensors scattered around the car) that work with the active cruise control and allow the car to be driven completely autonomous for 30-second intervals. Now, it's not quite as advanced as some of its competitor's systems - it can't change lanes for example - but if you're out on a country road or on a highway, it will stay within its lane, turn around corners and keep up with the traffic, even if they stop in front of you.

This is a full-size sedan, and every seat feels spacious and airy.

While the cheapest diesel model has historically been the best seller, BMW is hoping the new 530i will prove the most popular this time around. And while you couldn't describe it as fast, the power from its four-cylinder engine is ample for all that will likely be asked of it, and it feels sorted and composed on  more challenging roads. It's a smooth and comfortable ride, too, even with the optional 20-inch alloys fitted, though that's undoubtedly thanks to the adaptive dampers and ever-changing dynamic ride function, both of which are fitted as standard. In fact, we're yet to drive a car without those options fitted, so we're forced to reserve judgement on the as-standard ride quality of the cheaper models.

Be warned though, none in the 5 Series range offer the disconnected and perfectly smooth conveyance you might find in some true luxury offerings, and you'll still know when you're diving into deep pockmarks in the road. But the trade off is a an engaging ride and steering set up that always feels planted, with enough feedback to ensure you feel connected to what's happening beneath the tyres. And that's a trade we're more than willing to make.

Step up to the 540i and things take a much sportier turn. The turbocharged six-cylinder feels right at home in a car this size, with acceleration effortless and freeway overtaking manoeuvres an absolute breeze. And while we didn't find roads quite brutal enough to really test the active anti-roll bars housed at each axle, there's a wonderful and stable flatness to the way the biggest petrol handles corners.

It's not cheap, but thanks to the bigger engine and sorted dynamics, the 540i feels most like a 5 Series probably should.

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.

The BMW 5 Series is covered by a three year, unlimited-kilometre warranty, and requires condition-based servicing (rather than a pre-defined service interval).

You can also prepay your maintenance costs for five years/80,000kms, with prices ranging from $1,640 for the basic package, and climbing to $4,600 for the all-inclusive option.

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.