At nearly 5m tip to tip and with a wheelbase shy of 3m, the latest Mercedes-Benz CLS is a luxe barge shaped like a coupe
Mercedes-Benz CLS450, Mercedes-AMG CLS53: Sleek refinement The Mercedes-Benz CLS450 is driven by a turbocharged 3-litre inline-six, among the first petrol inline-six found in modern Mercedes cars. PHOTOS: MERCEDES-BENZ

With Audi unveiling its second-generation A7 Sportback this month, the release of the new Mercedes-Benz CLS could not have been more timely.

The first "four-door coupe" when it was launched in 2003 is into its third generation. It has a cleaner and more chiselled design. With its shark nose front end, it is also the most aggressive-looking CLS.

At 4,988mm, the car has grown by 48mm, with its wheelbase stretched by 69mm to 2,939mm.

The longer wheelbase definitely improves interior space but, more significantly, the CLS can now accommodate three adults in the back row.

The CLS is the first Mercedes with illuminated air-conditioning vents. There are 64 selectable colours and the vents glow momentarily if you adjust the temperature.

The CLS has never been short on refinement, but the latest model takes this up to another level. There is an optional Acoustic Comfort package, with laminated windows.

Key to the CLS450's performance is its new mild hybrid powertrain. It consists of a turbocharged 3-litre inline-six - the first petrol inline-six among modern Mercedes cars after the facelifted S-class - making 367hp and 500Nm paired with a small electric motor and a 48-volt power supply. This contributes an additional 22hp and 250Nm for brief bursts.

The facelifted S-class was the first modern Mercedes to have an inline-six engine, but the Singapore versions are powered by V6 units.

Driven in anger, the CLS450 will go from rest to 100kmh in 4.8 seconds. The scenery whooshes by in a blur, but as you come to the first bend, you immediately realise that tearing up mountain roads is not the car's forte, despite its all-wheel-drive set-up.

Its nose feels vague as you turn into a corner. Push harder and its 19-inch tyres start squealing as they struggle to latch onto the road.

The AMG CLS53 is more capable. Packing 435hp and 520Nm (it also has an additional 22hp and 250Nm in electric boost), the car completes the century sprint in 4.5 seconds, and its throaty exhaust soundtrack is more forthcoming.

With a firmer suspension and fully variable torque distribution (as opposed to the CLS450's fixed 45/55 per cent split between front and rear axles), the CLS53 corners better and is more nimble on the whole.

But the most agile variant may well be the one powered by a turbocharged 2-litre four-cylinder engine, which Mercedes says is capable of 295hp.

I had only 10 minutes with the rear-wheel-drive car, but it proved to be a refreshing drive. Unlike its two more powerful siblings, it actually enjoys being flogged.