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Flagship Audi adds hybrid power to its arsenal of advanced technology - but is that enough to knock the excellent Mercedes-Benz S-Class off its perch?

lmost three years have passed since the fourth-generation Audi A8 arrived as the brand's latest super-limousine and new technological flagship, and yet somehow we’re still to subject the Audi to full road test scrutiny.

This week, that changes, although we should say that an all-new Mercedes-Benz S-Class will enter the frame this calendar year, and so whatever the verdict today, life is sure to get more arduous for this enormous and outwardly impressive Audi.

Part-electric A8 cuts a subtle figure among its range-mates but, in Volkswagen Group fashion, gets a piercing LED signature in the front bumper that gives away its hybrid status.

This particular version is the recent 60 TFSIe quattro, the first A8 plug-in hybrid powertrain in the model’s 32-year history. It adds a potent and clever petrol-electric powertrain to an already long list of technological innovations, including level-three automation (that is, the car can manage its direction and speed within its lane) and the suspension’s ability to ‘stress or relieve’ the loading on each wheel by using individual actuators and smooth out the ride over inconsistent roads.

Both features are made possible by Audi’s new zFAS nervous system, which collates the inputs of 24 sensors and cameras dotted about the car and enables numerous further tricks, such as the chassis’ ability to rapidly tilt in the event of an impending side collision and take the brunt of the impact on its strengthened sills rather than the doors. Trivial developments these are not.

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And yet the fundamental requirement of any limousine that wants to topple the S-Class – something the A8 has never achieved but must be sorely desired in Ingolstadt – is world-class isolation and sublime rolling refinement. Time to find out where Audi stands in 2020.

The A8 range at a glance

Audi flirted with four-cylinder power for the previous 2010-2017 generation of its flagship saloon (for the hybrid model). This time around, the lowest available cylinder count is six, rising to eight for the range-topping S8.

As an understated luxury limousine, the A8 goes without Audi’s dual-clutch gearbox in favour of a smoother-shifting torque-converter auto, within the casing of which our test subject’s electric motor is housed.

There has been talk of this A8 receiving Bentley’s W12, which would take power to around 600bhp, though we’re not holding our breath.

Audi A8 design & styling

With both this Audi A8 60 TFSIe plug-in hybrid and the 563bhp V8-engined Audi S8 arriving three years into the sales cycle, Audi has certainly saved its most interesting A8 derivatives until if not last then at least later. And with 443bhp and 516lb ft, neither does the most frugal car in the range lag too far behind the S8 in terms of performance.

It pairs a 134bhp electric motor, mounted within the housing of the eight-speed torque-converter gearbox, and Audi’s existing 335bhp turbocharged petrol 3.0-litre V6. Torque is split variably but permanently between the axles.

It’s the electric portion of the driveline – supplied by a 14.1kWh lithium ion battery pack sitting beneath the boot floor – with which the driver is first acquainted. Start the 60 TFSIe and it wakes silently, pulls away under electric power and will remain that way until its maximum zero-emission speed of 84mph if you’re gentle enough with the accelerator pedal.

Call for greater propulsive force than the motor alone can provide and the engine joins the fray, although with the battery fully charged and primed to deliver its 28.6 miles of official electric range, it should prove no hardship to drive the A8 60 TFSIe like an all-electric car.

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There are, of course, drawbacks to cramming two power sources into one car. At 2330kg, this long-wheelbase plug-in hybrid A8 weighs 335kg more than its V6-only rangemate and it is also considerably heavier than both the Mercedes S560e L and the BMW 745Le xDrive, which are its chief rivals.

The air-suspended Audi is also the longest car of this trio, which makes it all the more surprising that its wheelbase and boot capacity are the smallest.

Audi A8 First drives