Mercedes-Benz CLS400

The Mercedes-Benz CLS-Class has returned to Australia in third-generation form. The bodywork is more “boardroom” than “weights room” this time around, but the bigger news lies beneath the bonnet – peer under it, and you’ll discover Mercedes-Benz’s first petrol straight-six in more than two decades.

Packed with technology and offering the best interpretation yet of ‘mild hybrid’ propulsion, the CLS is here now in mid-ranking CLS 450 form. We test it on local roads for the first time.

WHAT IS IT?

It’s Benz’s ‘four-door coupe’, or more accurately a large sedan that allows form to lead function. The chopped roof costs a little headroom and it’s considerably more expensive than a similarly-sized E-Class, but practical considerations such as these are secondary for a design-led luxury car like this.

WHY WE'RE TESTING IT

This is the all-new third generation CLS-Class, and in CLS 450 form tested here it’s also the first vehicle to arrive down under with Mercedes-Benz’s box-fresh 3.0-litre petrol straight six.

MAIN RIVALS

Audi A7, BMW 6 Series Gran Coupe, Lexus LS 500

THE WHEELS VERDICT

From its frameless door glass to its opulent cabin to its low-slung bodywork, the CLS 450 oozes class in a big way. It’s not a case of style without substance, however, thanks to a supremely refined and electrically-enhanced turbo inline six and outstanding levels of comfort.

PLUS: Outstanding refinement, cabin quality, long-distance comfort
MINUS: Not as athletic as the numbers suggest, pricey

THE WHEELS REVIEW

IN 2005 Benz dropped a bombshell with its first-gen CLS. While ‘four-door coupes’ are thick on the ground these days, the term was truly alien at the start of this century. At least, it was until the CLS arrived on the scene.

Low-slung with a chopped-down glasshouse it looked impossibly stylish for its time, and the second-generation model that succeeded it in 2011 was similarly jaw-dropping thanks to more muscular surfacing and swollen guards. Now there’s a third iteration of the CLS formula, but the ocular impact this time around isn’t quite so mind-blowing.

Not because it’s ugly, mind you. The opposite in fact. It remains wide, long, and hunkered down over the tarmac, but the wild design language of the second-gen has been replaced by a more businesslike interpretation of Benz’s corporate look. It still looks great, just a little less extroverted.

The real great leaps forward are found under the skin. There’s a completely new six-cylinder engine under the bonnet, arranged in-line rather than in a V format. It’s a return to a configuration last built by Benz in the 1990s, but the M256 3.0-litre six-pot in the CLS 450 is a very different beast to those machines.

And not just because it sports a turbo hanging off to one side, either. Underpinned by a 48-volt electrical architecture, the M256 is augmented by an integrated starter/generator (ISG) that’s sandwiched between the engine and nine-speed automatic and can deliver up to 250Nm of extra torque when the accelerator is firewalled. Given the 3.0 turbo already develops a healthy 270kW and 500Nm on its own, the CLS 450’s total system torque of 750Nm is properly stonking. From rest, it’s enough to zip the 1940kg CLS 450 to 100km/h in a very respectable 4.8 seconds. It’s worth noting that there are no AMG badges on the bootlid, despite the 450’s impressive acceleration.

But it’s not speed that impresses the most in the CLS 450. It’s the silky seamlessness of this powertrain, and the effortless thrust it possesses.

That’s most in evidence when you slot it into the mode more commonly known as ‘kryptonite for motoring journalists’ – Eco. Sport and Sport+ might liven up the powertrain, increase the exhaust’s volume and stiffen the 450’s standard air suspension, but despite the ‘coupe’ tag this is no sports car – as our colleagues at Motor found out.

But in Eco mode, the CLS 450 transforms into one of the smoothest, quietest grand-touring devices around. It wraps S-Class refinement in a sleeker bodyshell, and while the rear seats are predictably short on headroom, the relaxed posture offered by the canted-back bench seat and generous leg and elbow room promise outstanding long-distance comfort. What’s more, that turbo straight six is virtually dead-silent at a cruise, ticking over just a smidge above idle in ninth gear at highway speeds and transmitting barely any vibrations into the cabin.

But the greatest party trick is the powertrain’s ‘sailing’ function, which shuts down the engine when coasting and decouples the transmission from the wheels to reduce friction. The 450 will coast in this way for a significant distance without dropping much road speed, and passengers will scarcely be able to determine what’s going on. The engine shuts down and re-lights so smoothly and instantaneously, that the only way you’ll tell the system is active is by watching the tachometer like a hawk.

Not only is it refined, but it’s also a boon for efficiency. With a claimed average of 8.7L/100km, the CLS 450 is more economical than you’d expect of an all-wheel drive turbo six-cylinder that weighs nearly two tonnes.

Sound too snoozy for your tastes? The CLS 53 will amp things up in November with a higher-output version of the M256 that features an electric compressor, 320kW, 520Nm (770 with EQ boost) and a zero-to-hundred of 4.5 seconds, but those simply searching for a car that typifies those Benz qualities of elegance and effortlessness need look no further than the CLS 450.

SPECS

Model: Mercedes-Benz CLS 450 4matic
Engine: 2982cc 6cyl, dohc, 24v, turbo
Max power: 270kW @ 5500-6100rpm
Max torque: 500Nm @ 1600-4000rpm (750Nm with overboost)
Transmission: 9-speed automatic
Weight: 1940kg
0-100km/h: 4.8sec (claimed)
Fuel economy: 8.7L/100km
Price: $155,529
Available: Now