A smaller V8 engine in Bentley's Continental GT see big cuts in fuel consumption and emissions, says Matt Kimberley, PA motoring writer

Four years ago Bentley promised a powertrain for the Continental GT that delivered 40pc lower fuel consumption and emissions than the W12 system of the day. The result is finally here, and while its raison d'�tre is efficiency it also represents something more exciting than that.

The reality these days is that cutting-edge efficiency technology has become a selling point even to buyers with the means to pay 'whatever it costs'. In building a supremely hi-tech, much less environmentally-unfriendly engine Bentley has incorporated some of the most advanced efficiency techniques available for internal combustion – within the boundaries of what their customers really want.

After years of development the result is a 4.0-litre V8, two litres smaller than the older W12 and cleverly turbocharged to deliver a huge 500bhp and 487ft.lb kick.

Its most intriguing facet is what Bentley calls variable displacement. It's a cylinder shut-off system that, when the engine is under low loads, cuts fuel to four of the cylinders to leave a 2.0-litre V4. Pressing the accelerator brings the other four pistons into play, and you just can't feel it working. Without it there's no way a range of more than 500 miles would be possible from a 90-litre tank of super unleaded.

There are plenty of technological flourishes in the engine and gearbox, like mounting turbo chargers inside the 'V' of the engine to save weight and keep the key air flow pipes as short as possible. That way the turbos respond more quickly and there's no noticeable lag – remarkable for a 2.3-tonne car (nearly 2.5 for the convertible GTC).

There's also very little wind noise, whichever version you're driving. The GTC, like the coup�, is as quiet inside and it's easy to forget it's a soft-top. The roof also looks great both in place or folded away, which can't be said for all of its rivals.

Refinement is a big deal at Bentley, and certain well-known efficiency tech has consciously been left out because it'd take away from the element of luxury. It has the well-known and brilliant ZF eight-speed automatic gearbox but you won't find stop-start or eco change-up.

What you will find is a different character to the W12 engine. The Continental GT is a grand tourer, as per the name, but the GT V8 would better fit a 'grand sports tourer' tag. It's deliberately a little bit cheekier.

It's fair to say that performance is astonishing. The coup� hits 62mph from rest in 4.8 seconds, aided partially by the four-wheel drive's 60pc bias to the rear wheels. Top speed is 188mph. Through fast, sweeping corners it's incredibly well planted, and under the right circumstances feels a little bit alive.

It can't hide its chubbiness through tighter corners, where the suspension rolls noticeably even when turned up to its sportiest, but the coup� is still a compelling drive. The steering in the GTC is calibrated differently because of minor geometry changes on the chassis – the result is that it's too light .

The noise from the four exhausts, visually linked into pairs with open figure of eight shapes, is fantastic. It's a deep bass thrum with vague overtones of old propeller-engined fighter planes. The company has a good bit of heritage in the aviation industry and by making one exhaust longer than the other the engineers have created an off-beat burble that's rich, satisfying and unique.

Speaking of rich, satisfying and unique, the interior is customisable to taste. The highest-quality leather and wood is standard, but customers will have options on the finish of the gear lever, the materials used to upgrade the basic plastic steering column-mounted gear change paddles and the stitching in the trim – plus just about anything else.

The seats balance sporting support and cruising luxury. In its most comfortable setting, the suspension handles even horrendously-surfaced roads very respectably. Doubly so considering the 20in alloy wheels and low-profile tyres.

With its starting point as a 6.0-litre W12, Bentley perhaps had an easier task than some on the face of it to down-size and improve efficiency. By carefully choosing technologies to fit and complement the Continental GT, the result is a very credible and very satisfying new way to drive a Bentley.