There’s a choice of two petrol and three diesel engines, with an eight-speed automatic gearbox standard on all but the entry-level 1.5-litre diesel; this gets a six-speed manual, although the auto ’box is still an option.
A plug-in hybrid version of the 508, which combines a petrol engine with an electric motor, will be added to the line-up in autumn 2019. It should offer an electric-only range of around 30 miles, putting it in direct competition with Volkswagen's impressive Passat GTE.
Back in the present, though, the 1.5-litre diesel 508 feels underpowered, to the point where you'll find overtaking or joining a motorway more stressful than it should be. We have yet to try the 161bhp version of the 2.0 BlueHDi diesel engine, but the 174bhp unit has plenty of oomph and, like the 1.5, is reasonably refined.
For those who favour petrol power, the 179bhp 1.6 Puretech is smooth, responsive and a more spirited performer than the diesels, with the only disappointment being that it doesn't pull quite so well from low revs, so you have to work it harder.
The 221bhp 1.5 petrol brings a noticeable amount of extra oomph and is the quickest option in the line-up. But it's more expensive to buy and run than the lower-powered petrol, which is, on balance, the pick of the range.
Adaptive suspension is standard on the petrols and an option on the 2.0-litre diesels, with this linked to four driving modes: Eco, Sport, Comfort and Normal. Comfort and Normal tend to introduce a floating sensation over the crest of bumps at speed while Sport increases the steering weight and stiffens the dampers, but the differences are small. Regardless of setting, the 508 fidgets over road imperfections at all speeds; the Skoda Superb is far more forgiving.
The upside of the 508's firm set-up is that it resists body lean well in corners, in addition to gripping like a limpet. But it doesn't offer the steering precision of a BMW 3 Series, Ford Mondeo or Mazda 6, so you end up sawing at the wheel quite a bit.
The automatic gearbox can be hesitant around town (not helped by an overly intrusive start/stop system) but is otherwise impressively smooth and quick in its operation. By contrast, the six-speed manual that's standard with the 1.5-litre diesel is disappointing, because it has a long, notchy action.