Buyers can opt for one of four powerplants in the Infiniti Q50; the bulk of sales will no doubt be attributed to a Mercedes-derived 2.1-litre turbodiesel. There's also a 3.5-litre petrol-electric hybrid for those seeking a more serene experience backed up by some serious punch, while the petrol range is punctuated by 2.0- and 3.0-litre units.
Infiniti’s first four-cylinder diesel engine, despite its impressive origins, has not entered at the top of its class. There’s more to noise intrusion than simple numbers on a noise meter, and here’s a case in point.
The Q50 fires to an idle that registered 1dB less on our meter than a 320d did, but it seems louder and more irritating because of a prevalence of diesel rattle from which the powertrain, except at motorway speeds, never shakes loose.
It’s fine in low-throttle operations. Step-off is easily measured and the seven-speed automatic gearbox shifts smoothly enough around town and at a cruise. Expect more, though, and you’re likely to be disappointed. From rest to 60mph, the Q50 lags behind not just the 320d (8.7sec versus 7.7sec) but also the C 220 d (albeit by only a tenth).
We mention these figures not because 0-60mph sprints are regular features of a compact executive saloon driver’s day, but because they are a handy benchmark. We could just as easily have picked 30-70mph, through which speeds the 320d is 1.3sec faster than the Q50 (8.7sec).