The 2.0-litre HDi turbodiesel in the Peugeot 308 CC produces a peak 161bhp at 3750rpm, and 251lb ft of torque: a decent amount of thrust to pull along a car weighing 1736kg. On the open road, progress is stout without being outstanding; momentum takes a little effort to gain, but is more easy to maintain.
The HDi’s torque peak arrives slightly late by modern diesel standards, at 2000rpm, resulting in a slight pause in power delivery if the engine is revving below that point. You can partially mask this by selecting Sport, but the resultant low groan from a reluctant engine held in too low a gear soon gets wearing; while not outright noisy, this turbodiesel doesn’t make especially appealing sounds. Still, once past 2000rpm its pull is pleasingly consistent and relatively freely delivered to the 4500rpm limiter.
The six-speed torque converter auto ‘box teamed with Peugeot’s diesel engine performs tremor-free changes and is easily overridden with the manual mode, which, despite being designed for left-hand drive, is fairly convenient to use. The result is a civilised powertrain, if hardly a sporting one, but one that complements the CC’s cruising refinement well. Wind noise is contained to the point that, roof up, it’s easy to forget that this is a convertible at all, which is of course the point of coupé-cabriolets.
Peugeot’s 1.6 THP petrol engine makes for a distinctly more dynamic drive. Neither the 154- or the 197bhp tune is enough to make this substantial convertible feel like a sports car, but in petrol guise at least, the 308 CC’s engine is more flexible and smooth than the diesel, and seems reasonably pleasing on the ear. Economy is the obvious compromise; in the real world, while you could expect 40mpg from the 2.0-litre HDi, neither THP engine is likely to deliver an everyday return much beyond 32 to the gallon.
Although the economy claims may seem more appealing for the 1.6-litre VTi and HDi engines, both are best avoided. Although torquey enough in isolation, the 1.6 HDi makes for a driving experience too workmanlike to really suit the 308 drop-top, and the VTi simply struggles to motivate the car with any authority.