At very low speeds, the suspension is unable to prevent the effect of broken surfaces from entering the cabin. At these speeds the damping effect is so weak that the C6 begins to pitch and roll, though the damping regains control at higher speeds. At around 30-40mph the C6’s command over bumps and general control is exceptional. At motorway pace, however, it Is less accomplished. The damping firms up to improve body control and stability, but the trade-off is restlessness.
The steering's level of power assistance changes according to speed and driving conditions. Although it is finger-twirlingly light while parking and heavier at speed and in corners, there is precious little consistency.
There’s nothing wrong with the C6’s ability to cover ground – helped by ample grip – but it doesn’t have the agility of its more dynamic rivals, even with Sport mode engaged. That increases body control a tad, but you’re still aware that the C6, despite making a decent fist of cornering, wasn’t really engineered with this in mind.
The diesel engine is the same unit that you’ll find in the Jaguar S-type and XJ and the Peugeot 407 Coupé. Average economy of 22.7mpg during our test was disappointing and partly down to the C6’s 1951kg kerbweight. At least the engine’s power is delivered smoothly, driving the front wheels through a soft-shifting, six-speed automatic gearbox. The selectable override is, however, less obedient than you’d want.
It was wet and windy when we obtained the C6’s performance figures, but that would have made little difference – it is reluctant to spin its front wheels from rest in the dry. The C6’s 0-60mph time of 8.6sec is some way short of its rivals: the BMW 535d hits 0-60mph in 6.0sec, the Mercedes E320 CDi in a claimed 6.8sec.
Noise levels are low. The engine is all but inaudible at speed and road and wind noise are both well suppressed. The boot has an ample capacity of 488 litres, though access to it could be improved.
