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Think of an Audi A8 and you’re likely to imagine it being powered by a large petrol or diesel engine, so can a 2-litre petrol engine – even with an electric motor – really work in such a car?
Large, heavy luxury saloons like the Audi A8 have traditionally been powered by large petrol engines, and more recently, by large diesels. Diesels aren’t favoured in some countries or by some people, so Audi is offering a petrol-electric hybrid powertrain option in order to reduce emissions from its petrol engine.
The A8 Hybrid has a 2-litre TFSI petrol engine and an 8-speed Tiptronic automatic gearbox with a slim electric motor sandwiched between the gearbox and engine, complete with its own clutch, and an advanced lithium-ion battery.
The battery is in the boot, and it takes up a fair amount of space, reducing the boot space from 510 to 335 litres, and the fuel tank is also slimmed down from 90 to 75 litres.
Despite producing just 54bhp, the electric motor can power the A8 for short distances of up to 62 mph.
Sales figures suggest that Audi is obviously doing well with its understated design approach but we think that the A8 looks too similar to its smaller A6 and even A4 family members. In our personal opinion, the last two generations of A8 haven’t progressed in the styling department from an aesthetic point of view.
Interiors are something that Audi does very well, and the A8 cabin is a very pleasant place to be – even if, like the exterior, it isn’t hugely more upmarket than the A6.
Our test car was an ‘L’ version, meaning it had a longer wheelbase than the standard car, providing rear passengers with huge amounts of legroom.
Large luxury cars with powertrains designed for low emission running are generally not designed to be agile, responsive drivers’ cars, and the A8 Hybrid is no exception – it feels like a big, heavy car. However it’s an excellent way to cover long distances, when it’s extremely quiet and comfortable, despite the four-cylinder 2.0-litre petrol engine not being as silky smooth as larger V6 or V8 units. You’d expect the ride to be good, and the A8 doesn’t disappoint. The electric driver’s seat also provides a huge amount of adjustment to give a good driving position.
The transmission has Drive and Sport settings, with Sport keeping it in a more responsive gear. There’s also an EV button to hold it in electric-only mode.
You can change gear manually using the steering wheel-mounted paddles, but it’s unlikely that this car would be driven using manual shifts.
Gearchanges are usually smooth but the transmission can occasionally be caught out, resulting in somewhat snatchy changes. It’s also difficult to select reverse gear as it can be easily passed when shifting back up through the gate.
The A8 ended up travelling on a ferry to the Isle of Arran, when there was concern that a car with such a long wheelbase would be grounded on the steep ramps, but thankfully it survived unscathed.
An approach taken by other manufacturers – and by Audi itself with its diesel-hybrid Le Mans car – is to power one axle with the petrol or diesel engine, and the other axle with the electric motor. However the A8 Hybrid is purely front-wheel drive, a solution that reduces the complexity and weight of the hybrid powertrain, however it doesn’t give it the traction of a quattro system, which can result in wheelspin out of wet junctions thanks to the torque from the hybrid system.
The standard A8 hybrid returns 44.8mpg along with 147g/km CO2 emissions. Our long wheelbase test car had only slightly higher emissions, at 149g/km CO2.
It may be of no surprise to learn that the most economical driving speed is at around 50-60mph. Hybrids are generally very economical in urban areas, however the weight of the A8 counts against it in this environment, as it takes a lot of energy to get the A8’s mass of almost 2 tonnes moving again once stationary.
Weight is a common issue with hybrids – although the hybrid system can deliver fuel savings, the extra weight of the hybrid system can offset the savings under certain driving patterns that are outside of the paramaters of the NEDC test.
Our test showed that the A8 can achieve 40mpg if driven at a maximum of 70mph on a motorway. Urban cycle driving resulted in 24.7mpg. Overall we averaged 35mpg. This is some way short of the official 44mpg, but not a bad result for a large petrol luxury car. If you drive the car hard its weight will help drag the fuel economy down to the low 20s.
Despite the space that the hybrid battery takes up, it doesn’t have a huge capacity. You can see the hybrid battery charge gauge increase when braking, but even when full it doesn’t provide much electric-only running. A ‘hold’ function would be useful, to enable you to save the battery charge in normal driving for urban areas.
An Audi A8 with a hybrid system doesn’t come cheap. The standard A8 Hybrid costs £61,580; the L version costs £64,765.
The A8 is well equipped to start with, with standard equipment including climate control, leather upholstery, DAB digital radio, sat nav and xenon headlamps with LED daytime running lights. Then there are the options. Our test car had leather, comfort seats (£1,175), power door closure (£460), mobile telephone preparation with Audi connect and Bluetooth privacy handset (£830), digital TV reception (£1,000), privacy glass (£390), piano black inlays (£850), additional reading lights (£280), resulting in a total cost for the test model of £70,535.
If you don’t fancy the hybrid, then there are 3.0-litre and 4.2-litre diesels, 3.0-litre and 4.0-litre petrols, and a 6.3-litre W12 petrol. The 3.0-litre diesel starts at £53,685, and has an official combined economy figure of 46.3mpg, and the W12 L costs £95,440. Models at the lower end of the range have front-wheel drive, with higher spec models having quattro four-wheel drive.
The Audi A8 Hybrid is an interesting test to see if such a large luxury car can be propelled by a relatively small two-litre petrol engine, even if it is assisted by an electric motor. The A8 passes the test, although you don’t get the sensation of a large, lazy V6 or V8 petrol engine, and predictably the fuel economy in real life is somewhat short of the official figure. In reality most buyers in the UK will gravitate towards the TDI, probably the 3.0-litre model, rather than the hybrid. The diesel option is likely to be more economical, and starts at a cheaper price than the £61,580 hybrid. However more attention is likely to be paid to the A8 Hybrid, and other hybrids, as the focus on local air quality increases in cities such as London, and as tax incentives continue to favour such powertrain technology. In the meantime, despite its minority appeal, the Audi A8 Hybrid is an interesting and overall competent technical achievement and is awarded a Green Car Guide rating of 8 out of 10.
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Paul Clarke, GreenCarGuide Editor
