Fifty-three, then. Not 63, not 43 and, heaven forbid, not 65.

The new Mercedes-Benz CLS – the sleek four-door coupe now into its third generation – is here, and the rapid AMG variant, the 53, is almost as significant as the fact that the car itself is new. Let’s deal with the CLS bit first.

It’s a new CLS, which means it sits on Benz’s large-car platform with frameless windows and seating for five. It’s also promising to do the same ‘sleeker E-Class thing’ it has done for the past 15 years.

On some models, a 3.0-litre straight six-cylinder engine becomes the AMG 43, while there’s also the 4.0-litre twin-turbocharged V8 we all now know as the 63. Between these, AMG reckons there’s enough room to slot a 53 derivative. Whether a particular car will get 43, 53 or 63 options will, ultimately, be at AMG’s whim.

The 53 powerplant is a 3.0-litre of extraordinary complexity. Deep breath. It’s an inline six-cylinder petrol, mounted longitudinally, all of whose exhaust outlets pass through a single, large, twin-scroll turbocharger mounted high and next to the exhaust ports.

The inlet for that compressor comes after the big turbo, where a variable stopper in the main inlet tract, which runs around behind the engine, can divert a little, all, or any combination of air through a smaller tube to the electric compressor, after which, suitably pressurised, it flows back to the main inlet tract just before a throttle butterfly. Still following?

Anyway, it makes 320kW and 520Nm, which is quite a lot in itself. But in addition to both of these forced inductors, mounted between the engine and the nine-speed automatic gearbox sits an integrated starter/generator (ISG), an alternator/starter motor and flywheel combo, which can contribute 16kW and no less than 250Nm to the engine’s already imposing output.

Look, I don’t know, my head hurts with all the trickery. I suppose the short of it is that getting air through the engine is key, so inlet pressure rather than engine speed itself is king.

Ultimately, though, all of this power goes to the CLS’s rear wheels most of the time, with a standard all-wheel drive system on all models diverting it to all four when the rears threaten to slip. Unlike, say, the E63 S AMG, you can’t lock the 53 into rear-drive mode for adolescent slides. Which is perhaps just as well.

One of the challenges of the 53 was, by all accounts, to make it feel sufficiently different from a regular CLS to satisfy AMG boss Tobias Moers, who’s quite particular.

Full-fat AMGs do have quite a distinct character: they’re loud, brash and way more capable these days than the hot rods they were a decade or so ago but still dominated by their V8 engines. That’s a harder character to inject with a straight six, obviously, especially one whose exhaust is so muted by the turbo and which, by definition, is a bit semi-skimmed next to a 63. But the engine is sparky.

It’s a belting engine, in fact. I wonder if Aston Martin, part owned by Daimler as it is, has thought about one day dropping one into a Vantage…

And if regular wheels and tyres – 20-inch and 21-inch will be most buyers’ norms, we suspect – sharpen the steering over these winters, it’ll be intensely responsive for a big sedan. Okay, okay, big coupe. Because accuracy and steering response are already great.

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Air springs, although optional rather than standard as they are on the AMG, were also fitted to the two other CLSs I’ve tried – one being the wickedly fast 400d, with a 3.0 straight-six diesel, 250kW and the new EQ Boost system.

Whatever engine your CLS comes fitted with, though, it makes no difference to the way it feels inside, which is little short of excellent.

Headroom in the rear is, obviously, a bit tighter than in a conventional saloon, for the passengers you probably won’t have anyway, and the boot’s of a similar ‘yeah, fine, whatever’ capacity. If it’s not big enough, there’s always the E-Class, which is handy.

Overall, whether equipped with a lesser engine or with the new AMG 53 unit, the impression you get from the CLS is one of slickness. Even the 53 is never in-yer-face, never urging you to go harder or, in Aussie parlance, ‘begging to be fanged’.

Perhaps in grippier conditions, and on normal rubber, the 53 would feel more like a true AMG than it does to me here, but then I don’t mind if it doesn’t. Perhaps I’m less picky than Moers, because it strikes me there’s not a lot wrong with it the way it is.

2018 MERCEDES-AMG CLS53 SPECS: Engine: 2999cc inline-6, DOHC, 24v, turbo Power: 320kW @ 6100rpm Torque: 520Nm @ 1800-5800rpm 0-100km/h: 4.5sec (claimed) Weight: 1905kg Price: $179,900

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