GoAuto 13/07/2006

DO owners of cars worth more than $200,000 actually need to worry about fuel economy?

We may be projecting a bit, but one imagines that in this stratosphere the actual day-to-day running costs of a luxury limousine are incidental to the ownership experience.

Perhaps not. But those that do think economy, or even care a little bit about the environment, will warm to Audi’s new A8 4.2-litre TDI.

Not only do you get a fully blown luxury limousine with acres of leather, all the gadgets and a German badge - but the A8 TDI throws in the latest-technology common-rail turbo-diesel V8 engine with piezo injection and a particulate filter.

Techno-files will love the engine details of the A8 TDI.

The compact 90-degree twin-turbo V8 is the latest in Audi thinking, featuring an engine block made of vermicular graphite cast-iron – a quick Google can explain it – which contributes to the engine’s light weight and strength.

The engine block weighs 62kg, and helps contribute to a relatively low (for a diresel) overall engine weight of 255kg.

The engine’s cylinder bores are treated using UV lasers in a special process designed to reduce oil consumption in the engine, as well as particulate formation during the combustion cycle.

Each of the V8’s aluminium cylinder-heads feature chain-driven camshafts and ancillaries for long-life and durability.

The same system also drives the oil, water and power-assisted steering pumps.

Twin intercoolers are positioned right in the airflow area below the headlights for best efficiency.

Lastly, after you’ve digested the technology details of the engine, then come the power and torque figures.

Although it is the output of 240kW at 3750rpm is sure to grab your attention, the V8 has incredible torque, delivering 650Nm to all four wheels between 1600rpm and 3500rpm.

This wide band of urge ensures effortless acceleration at any speed through any of the Tiptronic auto’s six speeds.

Using all of the twin-turbo engine’s brute force, zero to 100km/h takes only 5.9 seconds and the A8 will hit 250km/h, according to Audi figures.

Impressed yet? We were, and then we took the A8 TDI for a spin, over 650km around Tasmania.

The first thing that strikes you about the A8 is its size. The car is beautifully crafted both inside and out and before setting off it’s worth just acclimatising yourself to the leather-wrapped environment.

First of all, like other high-level limos, there are four suspension settings for the adaptive air suspension. You can choose between Automatic, Sport, lower-riding Dynamic to ultra-supple Comfort.

After fiddling with them we finally settle on "dynamic", the best for press-on driving, before wallowing in the superbly bolstered seats and marvelling at the level of detail, quality and ergonomics.

Even on the firmer setting, the A8 rides well, the TDI acquitting itself to all manner of road conditions. You quickly realise that despite its size, the A8 almost shrink-wraps itself around you in the manner of a much smaller sedan.

The added level of security offered by the all-wheel drive system is also appreciated.

We marvelled too at the car’s sophisticated electronics, which you expect in vehicles of this calibre.

The A8’s DSP system will avoid excessively frequent gear changes in selected modes. In Sport mode, the car will hold a gear even if the accelerator is released suddenly.

The ESP’s lateral acceleration sensor will also detect when the A8 is cornering, and how hard, blocking up-shifts until the car is through the bend. The whole point is to avoid unnecessary and inappropriate "hunting" through the gearbox.

Like its petrol cousins, the TDI covers all bases in the areas of refinement, equipment and luxury.

Perhaps the only black mark against the car is the overly-light steering. It’s fine for around town, but enthusiasts may expect more feedback and feel on the open road.

Push-on motoring too shows up the car’s relative bulk. At almost two tonnes, the A8, despite its aluminium spaceframe body, is a hefty vehicle. It must be remembered, however, that its rivals in this segment are also porky beasts, making the statement somewhat academic.

The weight becomes more of an issue through winding mountain roads, where there's noticeable weight transfer despite the best efforts of the active suspension.

Mind you, in a lot of circumstances we were pushing the A8 as quickly as a smaller sedan, so some kudos must go to the car’s well sorted suspension for giving the leather limo the on-road balance of a hot-hatch. Almost.

The A8 TDI may not have some of the final dynamic crispness of a BMW 7 Series, but there is really little between them when it comes to on-road composure.

The meaty 19-inch tyres offer loads of grip but never seem to intrude on the car’s ride.

Visually, the A8 TDI looks like any other petrol A8, which means solid, Germanic style with a hint of masculinity about it - and doors that shut with the resolve of a bank vault.

The large single-frame front grille is there, while at the rear two large-diameter tailpipes, pointing down rather than straight out, give a subtle hint of the car’s power.

Inside, the cabin is superbly equipped and finished and most drivers will find the driving position ideal. The four-spoke multi-function leather-wrapped steering wheel – electrically height and reach adjustable - feels good and the general ambience is high class.

Audi’s multi-media interface is also worth a mention here too. Unlike some other systems we’ve experienced, Audi’s MMI is intuitive and easy to navigate. The same goes for all the other switchgear.

The operation of the MMI’s LCD colour screen is a work of art.

It folds out from the top of the dashboard with a flourish, sitting high in the line of sight. When not in use it disappears at the touch of a button.

Rear passengers are not left out either. Rear seat legroom and headroom is good and there are individual controls for the air-conditioning, as well as plenty of storage areas. Lastly, the boot is huge with a flat load floor.

So, does an Audi A8 diesel fit the luxury segment?

Very definitely. Luxury buyers now have something else to brag about.