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 CLS 63 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

  • Jaguar XFR
    Not only is the XFR the class leader, it is also exceptional value compared to rivals

    Jaguar XFR

    1
  • Mercedes-AMG C 63
    Mercedes-AMG C 63 saloon is priced from £59,800

    Mercedes-AMG C 63

    2
  • BMW M3
    The M3 packs a twin-turbocharged 3.0-litre straight six that produces 425bhp and 405lb ft

    BMW M3

    3
  • Mercedes-AMG E 63
    The old 6.2-litre V8 has been dropped in favour of a twin-turbo 5.5-litre V8

    Mercedes-AMG E 63

    4
  • Jaguar XJR
    The Jaguar XJR offers monstrous, relentless performance

    Jaguar XJR

    5

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