Jaguar XJ 3.0 S/C premium luxury

Engine: 3.0 litres, six cylinders, supercharged
Top speed: 155mph
Price: £65,365
Power: 340bhp at 6500rpm
Fuel/CO2: 29.4mpg, 224g/km


This is an XJ with a supercharged 3-litre V6 motor under the bonnet and the first question it raises is who on earth will want to buy it. Compared to the turbocharged 3-litre V6 motor already available but fuelled by diesel, this one provides quite a lot more power (an extra 65bhp to be precise) but a great deal less torque (110Ib ft since you’re asking). By giving with one hand and taking away with the other Jaguar has managed, on paper at least, to create a car of very similar performance (their 0-60mph times are separated by 0.2sec) for a catastrophic cost in fuel consumption. The diesel will make a gallon go well over half as far again, which means its range is more than 50 per cent beffer too.

But that’s not the end of the issues: your first year tax disc in a supercharged 3-litre costs £600, but just £170 if you choose its turbocharged sister, and of course there are commensurate implications for company car tax as well.

Just as telling is the fact that the diesel motor is so much beffer suited to the XJ than the petrol unit. While the diesel allows you to waft along on a flex of a toe without the slightest need to use more than 2500rpm on any journey, HIS IS AN XJ WITH A supercharged 3-litre V6 motor under the bonnet the blown motor is more urgent, not just willing to rev but demanding to be rewed too. It’s quiet enough at a constant cruise, though certainly no more refined than the diesel, but the moment you want to power past some traffic, it drops several of its eight gears and throws the needle around the tachometer.

Actually this is not a bad engine. It’s just in the wrong car, and the wrong place. Imagine, for instance, you live in America where diesel is what you put in your Peterbilt and gas remains in real terms less than half what you pay in the UK. Compared to what else is available there, it would suddenly seem several streets more competitive.

More enticingly still, change not the country but the car and imagine this engine under the bonnet of an F-type, a car you’re going to want to thrash: suddenly you’re huffing 60mph in under 5sec, listening to the supercharger wail and all is suddenly well with the world. In theory at least: the proof of that particular pudding remains a month or two away.