A straightforward geometric extension of the firm’s four-cylinder engine it may be, but this 3.0-litre six is a supremely balanced device and sensationally quiet. As a consequence, there’s precious little by way of a sensory cue as the engine flicks in and out of dormancy while cruising along in the outside lane of the M4. The flip side is that this leaves you free to contemplate a ride that on 19in wheels is much improved over CLS models we’ve previously tested – ones touting 20-inchers – but still isn’t as good as you’d expect.
This AMG Line car breathes with the topography well enough despite a 15mm drop for its traditional steel-sprung suspension, but variations in the quality of the road surface intrude. There’s a fidget, a slight jostle and though it’s delicate enough to be put to the back of one’s mind, it’s hardly a trivial matter at this esteemed end of the market. An E-Class doesn’t do this, and neither does an Audi A6, but an A7 Sportback – the only true rival for the CLS – absolutely does. It seems beyond the wit of the manufacturers to safeguard ride quality when the car’s roofline gets a bit racy.
The interior is handsome, mind. Moreover, while there isn’t quite the same impression that you wouldn’t know even where to start pulling it apart (as you don’t in an A7 Sportback), it’s sturdier than we’ve become accustomed to from Mercedes. It’s also flamboyant. The slightly perched seats are bespoke for the CLS and mimicked in the back, which now has a central berth for the first time; grainy wooden trim encircles the cockpit in a manner that, along with the generous transmission tunnel, puts me in mind of the 550 Maranello; and the vents do a light show corresponding to the air temperature they’re vending. Along with privacy glass and the metallic paint, this car has but two options: the £3895 Premium Plus and £1695 Driving Assistance Plus packages.
The former includes the top-spec Comand Online infotainment, a 590-watt Burmester sound system, keyless go, a sunroof and Mercedes’ 360-degree camera, which is useful for a car longer, wider and taller than the one it replaces. The latter equips the CLS with a gamut of safety technology, some it useful (active blind-spot assist), some of it not (active lane-keeping assist, essential for half an NCAP star...). Shouldn't itbe thrown in for ‘free’ at this level? You might think so.
Our ride-related concerns notwithstanding, by the time those wide-spaced headlights are steering onto the meandering smoothness of the A479, the CLS has done precious little to discredit itself as a strident family grand tourer. Leading north- west from Crickhowell and into the startling green of Wales proper, it’s on this road that the Mercedes then cements itself as a worthy all- rounder. It goes unnoticed on the motorway but 362bhp and, more tangibly, 369lb ft from only 1600rpm is enough to give a two-tonne exec a slap-bang turn of real-world pace. This engine will spin to the 6250rpm redline, too, though you’ll find yourself inhabiting its torque-rich mid-range because that’s how a CLS 450 likes to be driven.