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Engine options, top speed, acceleration and refinement

Selecting Sport via the 508’s centre console-mounted switch elicits a handful of changes to its character. In addition to a moderately more responsive throttle and meatier steering, the synthesised engine note sounds like it’s being broadcast in the cabin in stereo, or at least as though it has been double-tracked.

Were it a particularly euphonious soundtrack, this would be a welcome change; however, given the grumbly, diesely timbre of the 508’s BlueHDi motor, the increase in volume isn’t a particularly welcome one, and it ends up coming across as a flawed attempt at making the engine sound bigger and richer than it is. At maximum revs in fourth gear, our sound gear recorded cabin noise at 74dB; by comparison, the Volvo V60’s D4 engine – which we criticised for being overly vocal – measured 73dB.

Slimline 508 sits more comfortably in its lane than three adults at the back might. Still, good road manners mean rear passengers shouldn’t be unduly inconvenienced

Still, straight-line performance is agreeable for a car in this class. A timed 0-60mph run of 8.8sec – compromised, perhaps, by a scrabble for traction off the line – is roughly par for the course, if a little behind Peugeot’s 8.3sec 0-62mph claim. The 187bhp Audi A4 TDI tested in 2015 did the same run in 8.4sec, while the 2012 BMW 320d managed 7.6sec.

However, with similar torque (295lb ft for the Audi and 280lb ft for the BMW), the Germans bettered the 508 from 30mph to 70mph – a more representative benchmark for real-world accelerative potency – by considerable margins. While the Peugeot took 8.5sec, the A4 managed 7.2sec and the 320d needed 7.4sec.

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Repeating the same run while locked in fourth gear – an indicator of an engine’s flexibility – took 9.7sec in the Peugeot, placing it between the Audi (8.2sec) and the BMW (10.8sec).

The manner in which this acceleration is delivered is generally smooth, although if you stray too far past 4000rpm, the diesel runs out of breath. One tester also commented on an apparent tendency for the eight-speed ’box to hold on to its gears for slightly longer than necessary above this point – a factor that could have contributed to the 508’s failure to meet or better its manufacturer’s 0-62mph claims.

Out on the road, the transmission goes about swapping cogs in a generally smooth and unintrusive way. The only times when a shade of indecisiveness was detected were at lower speeds, where there could be a degree of shunt when pulling away. On track, though, things weren’t so slick.