Although we’re generally remarkably impressed with the inherent efficiency of modern forced-induction motor, why is it that we welcome the 5.5-litre, twin-turbocharged motor in the CLS63 AMG with a mild sense of trepidation? 

Mainly because we’ve been so won over by the depth of character and performance of the naturally aspirated 6.2-litre V8 it replaces. However, this engine not only has more grunt than the 6.2-litre V8 but is also 32 per cent more efficient.

And in no installation does it make more sense than in the CLS. We already know the four-dour coupé to be excellent luxury transport, and as a sort of high-end enthusiast’s limo it can justify having 549bhp (in the Performance Pack model tested here) better than most other Mercedes. 

But there’s no point to having such extravagant outputs – or an equally extravagent price – if it’s not sensationally entertaining, as well as civilised executive transport. And that’s not an easily achieved compromise.

Top 5 Super saloons

First drives

Find an Autocar car review

Driven this week

  • First Drive
    3 March 2015
    Sharper handling, more refined and better-looking. Still a bit rough around the edges, mind, but now good enough to be a class contender
  • Car review
    27 February 2015
    The second pure Mercedes-AMG model is a triumph of engineering and design, and should have rivals from Porsche and Audi worried
  • First Drive
    27 February 2015
    Dual motors and a power hike give Tesla's electric family car supercar acceleration - and the rest of the package is as strong as ever
  • Car review
    26 February 2015
    Flagship performance C-Class is more than ever a true rival for BMW's M3, and impresses with both its breadth of ability and its practicality
  • First Drive
    26 February 2015
    The new Renault Megane GT 220 is essentially a toned-down version of the hallowed Renaultsport 275, but does it have the required DNA?