It is unfortunate that one of the cabin’s most conspicuous limitations is the uncouth and muted grumble that fills it every time you start the XF’s Ingenium engine from cold.
Criticism of the refinement levels of modern four-cylinder diesel engines is widespread – BMW and Mercedes-Benz have both been dragged over the coals in this respect – but Jaguar Land Rover’s new motor is similarly not quite up to snuff in this respect.
With the noise – a distant yet classic grind of unwarmed ironwork – comes a tepid pitter-patter of vibration, too. It’s insufficient to grind an axe on, yet begrudgingly noticeable when you ideally want to feel nothing from the dirty work being done up front.
Mercifully, with a proper working temperature under it, the situation improves noticeably. The XF remains voluble when toiling through the low gears, but the soundtrack settles well beneath the wind noise when you’re up to speed.
It’s a shame that working the car into a lather from a standing start isn’t quite as precipitous as it ought to have been. Jaguar quotes 7.7sec for the higher-powered model’s sprint to 60mph.
The example on test – two-up and brimmed with fuel – lumbered over the tape in 9.4sec at Millbrook. That’s not unreasonably slow, perhaps, but being behind the latest Skoda Superb over the same ground is cause for some concern.
Thankfully, the XF ups its game in later gears, the combination of a respectable 317lb ft of peak torque plus a multitude of available ratios for the gearbox mean that the car’s sails rarely feel anything less than wind-filled.
It is by this barometer – as well as efficiency, of course – that we ultimately tend to appraise modern diesel engines and, in the first respect, the Ingenium meets its brief well enough.
Nevertheless, the XF doesn’t qualify as a class leader from under the bonnet, and given JLR’s huge investment in that particular area, that is a disappointment.