If there exists something of a mismatch between the predatory aesthetics of the Q8 and this demure diesel powertrain, such is the car’s rolling refinement that for a large proportion of customers it simply won’t matter. With the benefit of optional double-glazed windows (negated in part by the echo-chamber tyres attached to vast 22in wheels, also optional), our test car’s cabin was only slightly more noisy at a 70mph cruise than that of a Mercedes-Benz S-Class.
Along with the conspicuously perched seating position and opulent cabin, the effect is profoundly becalming. When the 3.0-litre V6 finally makes itself heard – an event that only really occurs above 3000rpm – it does so with a remoteness found only in very large cars.
The cruising credentials of the Q8 are further established by a touring economy of a shade over 40mpg and a standard 75-litre fuel tank, giving a potential range of 660 miles between stops. Along the way you’ll find the engine shutting off entirely should you coast in a window between 30 and 100mph, with the 48V mild-hybrid system at other times recuperating energy through the brakes.
Incidentally, those brakes are excellent, should you ever need to exercise them fully. Full-bore stops from 70mph are over sooner than even Porsche’s latest Cayenne Turbo can manage, despite that car having 10-piston front calipers.
Elsewhere, the Q8’s superbly smooth engine is not as convincing as it is in the lighter A8. With its substantial fuel tank brimmed, our Q8 weighed 2285kg, which is a lot for any car, not least one with sporting pretensions. It’s a mass against which 282bhp and 443lb ft could only yield a 0-60mph time of 6.9sec, with 30-70mph – our overtaking metric – taking 6.7sec. For reference, those figures are healthy enough to show a Range Rover Sport TDV6 a clean rear skid-plate, but equally, even the 3.0-litre TDI Q7 we road-tested in 2015 proved quicker on both counts, despite its power deficit.
Those who desire performance more on a par with even the latest hot hatches, let alone the quicker SUVs, should therefore wait for more powerful petrol and plug-in hybrid Q8 variants.
For everybody else, this 50 TDI unit will not only suffice but will do so with a surfeit of class. Our only significant criticism stems from a vacuum of torque beneath 1900rpm and the eight-speed torque-converter transmission’s sometimes lethargic kickdown efforts. The combination can make sharp progress at short notice a frustrating enterprise.