IT'S THE SOUND that disconcerts. For when I fire up the latest edition of the Jaguar XJ, what emanates from beneath its elegantly sculpted nose is neither a feline purr nor a burbling growl, but the kind of unprepossessing buzz that I'd expect to hear from a taxi rather than a refined limousine with definite sporting pretensions.
Yes, I know that the British company has ploughed a highly individualistic furrow in its response to the S-Class Benz, 7-series BMW and Audi A8, by endowing its flagship with unorthodox coupe-like styling and unique features such as its virtual instrument display. And I'm equally aware that downsizing engines is clearly the way of the future in most segments of the car market. But can Jaguar really be serious in fitting an inline four-cylinder engine beneath the bonnet of its top-end contender, in place of a silky V6 or the thumping great V8 that powered the last XJ I drove?
Evidently the guys at Gaydon are very serious indeed – and when I do take the time to peruse the figures, I have to admit that they make more than a modicum of sense. Of course, XJ buyers can still choose from a wide range of petrol engines, from a 271bhp, turbocharged 3-litre V6 all the way up to the bonkers, 500-plus-bhp, supercharged 5-litre V8 that's available on the car's Supersport and Ultimate variants. Yet Jaguar also manifestly believes that the entry-level Luxury version's standard 2-litre inline fourpot is easily up to the task of hauling this 1.7-tonne luxo-barge about.
With twin variable camshaft timing offering impressive power, economy and emissions, balance shafts to reduce vibrations and a turbocharger to further enhance performance, the XJ's lightweight aluminium motor is essentially the same Ford-built EcoBoost unit that's already found on vehicles as various as the Range Rover Evoque, the Ford Focus ST and Jaguar's smaller XF sports saloon. (Under a deal between Jaguar Land Rover [JLR]'s previous owner, Ford, and its current proprietor, India's Tata Motors, the former will continue to provide engines until 2019.)
As installed in Jag's biggest car, the power unit produces a more than respectable 237bhp, as well as 340Nm of torque – numbers not so far removed from those of the 3.5-litre Mercedes S-Class, which crucially weighs in at some 250kg heavier than the all-aluminium British rival. Transmitting this power to the XJ's rear wheels is a new ZF eight-speed automatic gearbox – controlled by the now-familiar circular JaguarDrive Selector, as well as a pair of steering-wheel paddles – whose abundance of ratios and choice of normal, dynamic and winter modes should help bridge any gaps in power delivery arising from low-speed turbo lag.
In most other respects, however, the test car pretty closely resembles the 5-litre version that I drove a couple of years back. And though I've had ample time to get used to it, I have to say that I'm still not completely sold on the XJ's looks. Granted that it's bold (brave, even), has massive presence and is certainly distinctive – this big Jaguar will never be confused for one of its German opponents, which is surely a recommendation in itself – but I'm still not entirely convinced that the relatively short front end and long, low roofline quite belong together in the same design.
On the inside, however, it's very different, for few passenger cabins manage to meld luxury, elegance, drama and modernity quite so masterfully. From the driving seat the view is spectacular, with a great sweep of dashboard topped by a wood-accented horizon line that links both sides of the compartment, and four gleaming circular air vents – one at each side and a pair flanking an exquisite analogue clock in the central binnacle – that still to these eyes resemble the jet intakes of a 1950s bomber aircraft.
Strapped into a large and accommodating leather chair with my hands at quarter-to-three on the lovely soft-leather steering wheel, this is a cool and commanding place to be – though I would prefer to be referring to actual instruments than the XJ's virtual display, and I have seen more user-friendly touch-screen infotainment systems than this rather fiddly device sitting above the centre console. Lavishly appointed, and beautiful to touch and to look at, the cabin whispers money and class, even if those riding in the back might wish for a smidgeon more room above their heads.
Almost as soon as I get it rolling, any doubts I've harboured about this beast begin to vanish, notwithstanding the unexpected noises from the engine bay. I remember the XJ as being far wieldier than its size (5.12 metres long, 2.1 metres wide) would suggest, yet this latest one is revelatory. Aided by its superb chassis, fluid ride and precise – if perhaps a shade too light – steering, it feels nimbler than it has any right to.
True, in terms of outright urge it's comprehensively outgunned by its biggerengined siblings, yet this monster can still be punted around so easily that it sometimes verges on the surreal. You can put that down to the fact that it carries substantially less front-end weight than the V6 or V8 models, which surely translates into better balance on twisting tarmac.
While performance is brisk rather than shattering, the car is no slouch in either city or highway traffic. From a standstill, 100km/h appears in 7.5 seconds, while its maximum speed in excess of 240km/h is at least double the absolute limit in most countries. Expressway cruising is relaxed and quiet, the rev-counter needle hovering around the 2,000rpm mark on the TFT display, and when I later point the Jag up the steepest gradients I can find, I have a hard time discovering any shortcomings in the way the four-cylinder motor delivers, apart from the anticipated turbo lag. That is easily remedied by a couple of flicks on the lefthand paddle-shifter, returning the engine to a more useful spot in its power band.
As I begin to revel in its agility and poise, I ask myself whether a bigger motor would make the XJ more appealing, and better suited to urban conditions. To my mounting surprise, the answer to both is negative.
Crucially in this age of declining resources and rising fuel costs, the 2-litre XJ drinks petrol at the rate of 13.6 litres per 100km in town, which though considerably more than the diesel's admirable 7.1 litres, is certainly less thirsty than the V8. Add to that its lower price, and the fact that its smaller engine slots the car into a much lower tax bracket than the majority of its luxury rivals, and the Jaguar represents a persuasive proposition in terms of numbers alone.
But that's not the reason I'm most impressed by this newest XJ. I'd been thinking that JLR had lost the plot by so radically reducing its engine size, yet after mere hours at the wheel I'm not only converted but seriously questioning whether this characterful and sophisticated automobile needs any more power than this.
Word has it that if Jaguar can get its hands on enough of them, the exemplary EcoBoost will eventually find its way into the eagerly anticipated F-Type roadster. Now that really would be worth waiting for.