The latest iteration of the Porsche Panamera is not so much a facelift as it is a "butt-lift".

With a wider rear windscreen, a new boot lid and a more pronounced rear bumper, the car's rear section no longer appears as dumpy as before.

In fact, with a more swept-back windscreen, the car looks more the part of a sleek super saloon.

The most obvious modification must be to the front. The air intakes are larger, giving the car a more aggressive front section.

The sum of these minor changes results in an improvement that is most obvious in the metal. They go some way in addressing criticisms about the car's styling - in particular, its abrupt and inelegant rear - when it was first unveiled four years ago.

Unlike some manufacturers, Porsche never confines itself to cosmetic changes. The mid-life upgrade of the Panamera includes an expanded model line-up. New additions include a plug-in hybrid and new S variants.

Porsche has also taken the opportunity to downsize. A new 3-litre bi-turbo V6 replaces the previous 4.8-litre naturally aspirated V8 in the Panamera S and Panamera 4S.

The engine is punchier, yet more frugal than the V8. In the Panamera S tested here, it proves to be a sweet power plant that feels a lot bigger than its actual displacement.

It produces 420bhp at 6,000rpm, compared with 400bhp at 6,500rpm for the preceding engine. When called upon to unleash its full complement of horses, the V6 emits a rich, full-throated growl, accompanied by a convincing exhaust boom when you lift your foot off the pedal.

Porsche employs acoustic aids to enhance the engine and exhaust notes, which are most obvious when Sport mode is selected.

But the quality that is most endearing is its highly accessible torque. The new engine delivers a peak torque of 520Nm between 1,750 and 5,000rpm - up from 500Nm between 3,500 and 5,000rpm.

With this, the Panamera is a joy behind the wheel, whether you are running from meeting to meeting in town, cruising on an open highway or simply executing a clean getaway at the lights.

Most day-to-day tasks on the road are seen to at low engine speeds but when necessary, the V6 piles on the revs with gusto.

It feels uncharacteristically light and breezy for a big sedan.

Zero to a hundred is accomplished in 5.1 seconds, down from 5.4 previously. Top speed is 287kmh, up from 283kmh.

Like all Porsches, the Panamera is blessed with sharp and responsive steering. It is weighty yet effortless, communicative yet not in the least twitchy.

Together with the new engine, it makes for a more dynamic drive.

Despite its improved performance, the Panamera S is more fuel efficient than its predecessor. But the improvement is not all due to the smaller engine. The car's dual-clutch transmission has also been endowed with "intermediate virtual gears". This essentially means lower revs at light-load conditions.

Porsche has also enhanced its automatic stop-start function to cut off the engine when the car is coasting to a stop.

Owners here will save on road tax too. With the smaller engine, they pay $2,382 a year, less than half the amount the V8 attracted.

The test car has features befitting a luxury limo, such as soft-closing doors, comfort-access driver's seat and motorised tailgate.

Strangely, it does not have keyless access and ignition. Even more strangely, its Hold function activates the parking brakes only when the car comes to a stop on an incline.

Alas, most of these are options you have to fork out more for. It does not help that higher taxes have made the car a lot costlier than four years ago.

On the bright side, the car is better- looking, more powerful and incurs lower running costs.

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