Contrary to what you may expect, the Mercedes-Benz E63 AMG never had a 6.3-litre engine – the old car packed a naturally aspirated 6.2-litre V8. Now the powerplant has shrunk to 5.5 litres but sprouted a pair of turbochargers. It is the same V8 mill already found in the CLS63, S63 and CL63 AMG.

In standard guise, the blown unit develops 549bhp. Torque has risen by a healthy margin though, jumping from a 464lb ft in the old atmospheric engine to 530lb ft at just 1700rpm, or 3500rpm earlier than before.

Deputy road test editor
It may be expensive, but it's one of the best high-performance executive saloons on the market

As part of the 2013 facelift of the E-class, Mercedes has dropped the old Performance Package option and provides instead the new E63 AMG 'S' version, with upgraded engine management and intake systems.

It introduces an additional 0.3bar of turbocharger boost pressure, among other measures, in a move that raises output to 577bhp at 5250rpm, while raising torque to 590lb ft. Emissions from the Mercedes remain unaffected.

During the same model-year changes, revisions were made to the E63's suspension and steering systems, which supply added grip, directness and feedback for the car. This is still a big Benz with air suspension in the mix, and so it does comfort more than well enough. But now it also does involvement and feel as well as any fast four-door.

The car's handling still isn't as naturally sweet or precise as a Jaguar XFR's beyond the limit of grip, but it is hugely enjoyable and, it almost goes without saying, endlessly driftable. And there's a glittering surplus of old-school hotrod character here. There aren't many new-breed executive saloons – with electromechanical power steering and state-of-the-art stability controls – that communicate so honestly and so vividly.

The performance of the new turbocharged engine is clearly more accessible than that of the old naturally aspirated unit, which needed to be stoked up before delivering its best. The defining characteristic is the enormous flexibility that is created, which reminds you of the way AMG's old supercharged '55' engines came on song. At pretty much any revs, in any gear, there is vast thrust. Speed builds quickly and, owing to the smoothness of the delivery, rather deceptively.

To experience the full force of the E63’s new engine, you need to call up 'Sport Plus' mode. Do so and you discover the reworked gearbox picks off gears with greater speed and precision than before thanks to improvements in the mechanical clutch and changes to the Speedshift software package controlling it.

Mercedes-Benz claims the standard E63 saloon, which weighs 1845kg, hits 62mph from a standstill in 4.2sec, or an even sharper 4.1sec as the E63 'S'. This makes it up to half a second faster up the strip than the old model, whose engine was available in just a single state of tune. 

Top speed, like all AMG models, is limited to 155mph, although the Driver’s Package option, which also gets the buyer a day of high-speed driver training, bumps it up to a limited 186mph.

Given the heroic performance, the new E63 is reasonably economical, too. Official figures suggest it’ll return 28.8mpg on a mixture of city and motorway driving for an improvement of 4.5mpg over the old E63. In the real world, though, the figure is closer to 24mpg. Go for broke and it quickly dips below 20mpg.

The E63 is capable of shaving 10 seconds off the old model's lap time at the Nürburgring, bringing it under eight minutes for the first time. Not too shabby for a car that can carry five adults and a nominal 540 litres of luggage in saloon guise, rising to 695 litres for the estate.

With all the regulatory measures in place today, it is becoming hard for British buyers to justify owning a car like this. However, those in the market for a rapid four-door saloon or estate should find everything they're looking for in the E63, and more. The changes AMG has brought to its latest model make it even more likable and rewarding, while extending its already haughty performance potential and providing it with impressive fuel economy when driven at posted limits.

It's not cheap, of cours – nigh-on-600bhp super-saloons rarely are – but it is worth the outlay. The E63 AMG is nothing less than the best mid-sized performance exec on the market right now, Jaguar XFR-S included.