Audi claims its updated 2008 A8 range includes the UK's 'cleanest' luxury sedan.

A new 2.8-litre FSI V6 version with updated valev lift system and 199g/km CO2 output is the highlight of the new line-up, available to order from late August priced from GBP49,995.

Styling, equipment, ride and handling and refinement have been updated range-wide as well.

The new 2.8-litre engine develops 210PS of power and torque peaks at 280Nm at 3,000rpm. Combined-cycle 'official' fuel consumption is 34mpg but the CO2 output of 199g/km enables that A8 model to comprehensively undercut both petrol hybrid rivals in the luxury segment and all diesel alternatives, Audi claimed.

The new engine made its debut in smaller A6 line earlier this year and is joined to a unique-in-class multitronic CVT automatic transmission.

FSI enables exceptionally precise metering of the fuel injected into the combustion chamber, ensuring that there is minimal wastage during each cycle, and the valve lift technology augments this by controlling valve opening far more precisely than conventional systems, improving fuel economy by a further 10%.

Valve lift is variable between two levels through the use of sliding cam units mounted on the intake camshaft. When strong acceleration is required, an electronic control mechanism selects a cam profile which opens the valve as fully as possible for optimum 'breathing'. When throttle usage is more relaxed, the control mechanism selects a lower profile, reducing the amount of fuel and air compressed.

Other 2008 mechanical improvements include re-engineering of the rack-and pinion speed-dependent steering to permit a more direct feel, and revision of the dampers, supports and general settings of the adaptive air suspension designed to give tighter body control through corners and an improved ride.

Supplementary insulation using new materials has also been added throughout the car, the result being that the A8 now claims the lowest rolling, road and ambient noise levels in its class.

DAB digital radio tuning has been added to the audio system and the climate control is upgraded to a more sophisticated four-zone system with individual temperature and air distribution controls. All UK models also get heated front seats, Bluetooth mobile phone connection and new trim materials.

Bi-Xenon headlamps are now standard range-wide, and there is a new grille, new exterior mirrors with integrated LED strip indicators and a new LED tail light arrangement. Sport models also feature a new alloy wheel design and S8-style bootlid spoiler.

New options include side assist and lane assist systems first seen in the Q7 SUV.