Road Test: Jaguar XJ 3.0d V6 Portfolio 4dr Auto

If you're the sort of devil-may-care British cad who's always fancied a caddish great V8 engine in your Jaguar... tough luck. The XJ's naturally aspirated 5.0-litre V8 is dead, gone, finito, replaced by a new supercharged 3.0-litre V6.

This shiny new V6 is not quite as powerful as the oily V8 it usurps, making 340bhp against the V8's 380bhp, and a handful fewer torques. But, as is the modern way, it's far more frugal and cleaner, returning a quoted 30mpg and a not-entirely-embarrassing 224g/km of CO2.

Jaguar, to its credit, doesn't refer to this decylindering as ‘downsizing' or anything so faddish: you feel the mpg improvement has less to do with saving cash and the planet, and more to do with reducing the time spent around sweaty proles at petrol stations.

Don't mourn the V8 too much (especially as there's still a supercharged version in the XJ-SS). The new V6 is a fine engine, smooth and strong and deceptively wild-eyed at high revs. It lacks the effortless low-end buffle of the V8, its relative paucity of torque exacerbated by the new eight-speed autobox's determination to slot into the highest gear possible at every opportunity, but it still sounds lovely (what little you can hear of it from within the hermetically sealed bunker that is the XJ's cabin: Jaguar has revised the spring rates and damper tuning to make things even quieter on the move, and though we'd be lying if we said we noticed the difference, the XJ is a very quiet place, even at *insert legal speed limit in your country here*.

And really, this is all the power you'll ever need to go in a five-metre limo: 0-62mph takes 5.7 seconds, just a couple of tenths down on the old V8. Still, if you're a truly British cad and not a foreign imposter, you won't be considering a petrol XJ, V8, V6 or otherwise. Everyone in the UK buys the diesel XJ - the one with Jag's lovely 3.0-litre V6: Jaguar expects fewer than one in 10 Brit XJ buyers to go petrol. This new engine is aimed squarely at China - where Jag sales have nearly doubled since last year - and America, where a V6 is considered the minimum requirement for a petrol engine (fewer than six cylinders and you're either a hippy or a communist).

But even though, unless you're planning on emigrating, you won't buy it in XJ form, there's another reason you should care about this tasty super V6. It'll also star in Jag's upcoming F-Type, the two-seat rival to the Porsche Cayman and Boxster. In a car as light and wieldy as the F-Type should be, the V6 will be a beast. In this state of tune, it's already making 15bhp and 59lb ft of torque more than the Porsche's powerful Cayman, the R. Brace yourself, Britain...