Parkers overall rating: 4.1 out of 5 4.1
  • Broad spread of engine talents with petrol, diesel and mild-hybrid
  • Entry-level motors plus 3.0-litre inline sixes at launch
  • AMG performance model offers the best of both worlds

The CLS was launched with three engine choices: two diesels – including the most powerful Mercedes-Benz has ever produced - plus a solitary petrol. All displaced 3.0 litres and had six cylinders, and came from the new modular generation of straight-six powerplants, with 4Matic all-wheel drive and a nine-speed automatic gearbox as standard.

Then the top of the range AMG 53 and entry-level CLS 350 and CLS 300 d followed, the latter from a new stable of four-cylinder engines promising both greater efficiency and driving enjoyment than those currently available.

Mercedes CLS diesel engines

The smallest diesel unit is badged CLS 300 d and is a 2.0-litre, four-cylinder motor with 245hp and 500Nm of torque - healthy numbers for an engine this size, although the 0-62mph time of 6.4 seconds is the slowest in the CLS range. Like the rest of the range it comes with an automatic gearbox as standard but two- rather than all-wheel drive.

Moving up there were two versions of the same six-cylinder engine (the CLS 350 d is no longer on sale) – a technically fascinating unit featuring exotic sounding tech like stepped-bowl combustion, nanoslide coating and variable valve-lift control. We won’t explain what those are (although we could, obviously) because in short what Mercedes-Benz is promising is the engineering holy grail – more power and better efficiency.

The CLS 400 d 4Matic delivers muscular excess in the form of 340hp at 4,400rpm and a tyre-smearing 700Nm of torque from just 1,200-3,200rpm. As we eluded to above, this is the most powerful series production diesel engine Mercedes-Benz has ever produced – so expect 0-62mph to flash by in five seconds flat and a top speed of 155mph.

To put it bluntly it’s an absolute sledgehammer of an engine with effortless acceleration from very low revs and a deep well of power held in reserve. It’s near silent while cruising and develops a menacing grumble when pushed. As such, it suits the CLS handsomely.

Mercedes CLS petrol engines

The entry point here is the CLS 350, a 2.0-litre, four-cylinder petrol engine that joined the range after launch. It uses similar EQ Boost tech as the larger six-cylinder petrol motors (described below), this time producing 299hp and 400Nm plus 14hp and 150Nm of electrical assistance.

The latter is deployed at low revs, again, to help torque-fill an area of comparatively low performance in a traditional combustion engine. It works well, although the CLS begins to feel its size while pulling off and accelerating in higher gears, where there is still a noticeable amount of lag. The noise it makes is quite gruff too, which feels a bit at odds with a luxury car.

Top of the normal CLS range is the CLS 450 4Matic – which is an inline six-cylinder with assistance from an EQ Boost electric motor and 48-volt electrical system. What does all of this do? Well, the electric motor, powered by energy otherwise lost during braking, is able to fill in the petrol engine’s power gap at low revs to offer seamless acceleration.

So on top of the 367hp from 5,500-6,100rpm and 500Nm between 1,600-4,000rpm produced by the petrol engine, you also get an extra boost of 22hp/250Nm from the electrical system. Unlike a full hybrid you can’t waft along in all-electric mode, but where possible the combustion engine shuts off so you can coast, before it’s quickly fired back up by the EQ Boost motor.

In Comfort mode its 48-volt system does a very good job of going about its business like a hybrid. The transition from engine off to engine on is imperceptible from the passenger seat – you only know when by watching the tacho. All of this points towards improved economy as well as speed and Mercedes-Benz backs this up with a bold claim - the CLS 450 4Matic provides the performance of an eight-cylinder engine with fuel savings akin to a high-voltage hybrid.

Its figures are certainly impressive – 0-62mph in 4.8 seconds and a top speed of 155mph – and claimed fuel economy that we’ve covered in the Running Costs section. The performance is noticeably more vivid than the diesels, which are muted and refined machines. When allowed to stretch its legs, the petrol CLS is a sportier, more responsive beast.

Mercedes-AMG CLS 53 4Matic+

Currently top of the tree in terms of performance (and length of badge) is the Mercedes-AMG CLS 53 4Matic+ - a standalone performance model, like those badged 43 within the C and E Class ranges, that act as an entry point to a full fat, V8 AMG model. Only there isn't one of those in the CLS range, because it's called an AMG GT 4 Door. Got it?

Mercedes-AMG CLS 53 driving 2020

This uses the same 3.0-litre petrol inline six-cylinder plus EQ Boost motor as the CLS 450 4Matic but with some future-gazing tech bolted on – enough for Mercedes-Benz to claim that this is the most sophisticated engine it has ever made. Power is up to 435hp at 6,100rpm and 520Nm of torque from 1,800-5,800rpm. Predictably that means a best-in-range 0-62mph time of 4.5 seconds and a top speed of 155mph.

Like the lesser petrol the AMG car also features an EQ Boost starter-alternator for a temporary lift of 22hp and 250Nm of torque, and 48-volt electrical system powering things like the water pump and air-conditioning.

How is it different from the CLS 450 4Matic? Well, it’s largely down to the extra boost of a special electric auxiliary compressor. This boosts turbo performance at low revs, which means you get even less lag, a more responsive throttle pedal, and plenty of get-up-and-go. The net result is heady performance and a nicely linear power delivery, plus an evocative exhaust note befitting of an AMG model. Although if we’re brutally honest, it’s not as soulful as the older 43-badged V6.

Automatic gearbox only

All variants of the new CLS feature Mercedes-Benz’s fast-shifting 9G-Tronic automatic gearbox, upgraded to an AMG Speedshift in the CLS 53. This promises imperceptible changes for comfortable cruising, or rapid-fire shifts when pressing on. A choice of modes from the Dynamic Select menu gives you a choice of Eco, Comfort, Sport, Sport Plus and Manual shifting behaviours ranging from languid to hasty.

The CLS 53 4Matic+ uses an AMG-tweaked Speedshift version of this ‘box, with faster paddle responses and double declutching function for multiple downshifts, so you can rapidly decelerate before a corner and ensure you’re in the correct gear for the exit.

Engines no longer available

The CLS 350 d 4Matic offered a respectable 286hp at 4,600rpm and 600Nm of torque from 1,200-3,200rpm. It could sprint from 0-62mph in 5.7 seconds and go onto 155mph – offering sizeable performance and good refinement. At idle there was some background low-frequency noise, but it pulled well from low revs, with just a muted growl, and cruised exceptionally quietly at UK speeds.

Handling

  • Standard springs, adaptive dampers and air suspension options
  • All work nobly to quell body movements and boost agility
  • 4Matic all-wheel drive claws into the tarmac with tenacity

Our first drive of the CLS meant dealing with a substantial amount of snow on the ground, and the standard-fit 4Matic all-wheel drive coped very well in challenging conditions.

Back in the UK and on more favourable tarmac we found the CLS grips very well indeed, offering huge traction from both ends of the car for confidence-inspiring levels of roadholding.

As a default the CLS sends 70% of its power to the rear wheels, so it feels nicely balanced when pressing on, and a clever electronic traction control system shuffles torque around so successfully Mercedes-Benz claims it doesn’t need to fit a limited-slip differential, which saves weight.

Steel suspension is standard

Your common-or-garden CLS comes with passive steel suspension as standard with the promise of a well-balanced ride and tauter handling than an E-Class saloon.

As an option you can select Dynamic Body Control adaptive suspension, which offers a broader spread of talents thanks to Comfort, Sport and Sport+ modes.

Finally there’s the top-level Air Body Control air set-up, which we were quite taken by. It’s not a cheap option but makes light work of rough roads and gives the CLS a wafty quality, without inducing seasickness. You can also pump it up by 15mm to traverse challenging surfaces.

Agile handling, despite size

The CLS uses a clever multilink front suspension system with lots of lightweight aluminium components to help enhance front-end agility.

As a result the coupe responds quickly to steering inputs and turns into corners with confidence – aided by electro-mechanical steering that varies its ratio in response to steering angle. Put shortly – the steering feels slow around the straight-ahead position and faster when wound all the way round.

There’s a lot of car here and as such bodyroll is inevitable. Happily it all happens in one go - the suspension and anti-roll bars stabilize the car quickly - so you don’t need to let the CLS settle for long before changing direction again.

Standard-fit Dynamic Select allows you to tailor the car’s responses and control weights, with increasingly performance-orientated Comfort, Sport and Sport+ modes on offer.

Anchor-grade brakes

Slowing a big, heavy car full of leather and wood is no easy job but thankfully the standard fade-resistant, internally ventilated CLS brakes are more than up to the job.

You also get Mercedes’ clever Adaptive Brake tech, which includes hill-start assist, automatic handbrake application and the ability to prime the brakes for an emergency stop when the car senses the accelerator being suddenly released.

They also dry themselves by wiping the pads against the discs periodically, to improve wet weather performance.

AMG 53 turns it up a notch

The sportiest CLS features much of the same tech as the standard car but with everything amplified for maximum driver enjoyment.

Mercedes-AMG CLS 53 profile driving 2020

All-wheel drive (now called 4Matic+) works faster to deliver traction where it’s needed most, while air suspension is fitted as standard with a specific AMG tune.

Adaptive dampers firm up the spring rate when cornering and braking to reduce body movements and geometry tweaks including more negative camber on the front axle improve cornering grip.

The steering’s a real highlight, an AMG hallmark, with a nicely judged weighting and level of feedback, plus in the car we drove, an alcantara wheel to hold onto.

The AMG CLS still feels like a big car but it’s noticeably sharper in all dimensions than the standard CLS coupe. We can’t wait to get one in the UK, with no snow and summer tyres.