The diesel engine. Audi has replaced the A8’s 4.0 V8 with this new common-rail 4.2-litre unit incorporating Piezo injectors, which allow fuel to be delivered at higher pressure and with greater precision.
This helps the engine develop 50bhp more than its predecessor offer a longer, flatter torque curve with a small improvement in fuel economy. It’s also 15kg lighter than the old unit.
Does the new engine work?
Sure does. If you were to conduct a blindfold test between the 4.2 and its petrol equivalent, we reckon many passengers would struggle to tell the difference, so impressive is the new unit’s refinement.
Drivers, however, will revel in the turbodiesel’s seamless punch from the foot of its rev range. The engine makes this A8 an even more accomplished mile-eater than its predecessor, particularly as Audi is claiming a touring range of up to 590 miles.
This aside, it’s standard A8 fare: the highlights are a comfortable, beautifully finished interior; the lowlights numb steering and a ride that isn’t as impressive as it should be given the car’s air suspension.