The new Infiniti QX50 has a petrol engine which is almost as efficient as a diesel
Best of both worlds: The new Infiniti QX50 The Infiniti QX50's engine is among the smoothest 2-litre four-cylinders around, matching the creaminess of a bigger power plant with more cylinders. ST PHOTO: ALPHONSUS CHERN

The Infiniti QX50 is the first car here to have a variable compression turbo engine, which promises the efficiency of a diesel and the punchiness of a petrol.

With the aid of an electric motor, a control shaft at the base of the engine rotates, influencing the angle of multi-link arms. This, in turn, changes the top dead-centre position of the pistons and thus the engine's compression ratios.

Depending on driving styles, the ratios vary between 8:1 and 14:1 to provide torque and efficiency respectively.

It involves a lot of moving parts. But surprisingly, the engine is among the smoothest 2-litre four-cylinders in the business, matching the creaminess of a bigger power plant with more cylinders.

Paired with a quick-acting continuously variable transmission, it delivers on its dual promise, albeit leaning towards performance.

Over the course of a three-day test-drive, the QX50 averages 10.5 litres/100km. Not bad for an all-wheel-drive weighing nearly 1.9 tonnes - but not quite the 8.7 litres stated in its specifications.

The Infiniti is quicker than its 8.3-second century sprint suggests. Squeeze its throttle with conviction and the mid-size sport utility vehicle hurtles towards its steered direction with the relentlessness of a charging elephant.

Steering response is sizzling, with a tautness which would not have been out of place in a hot hatch. Alas, the car's chassis is not tuned to optimise its torrential output nor its snappy steering. Its relative tallness and heft do not help.

Quick overtaking, as a result, can be slightly unnerving, with body roll in equal measure as you turn out and back in. At higher speeds, this sensation can be a tad unsettling.

A shame really since the QX50 is built on a new platform. With large wheels set at the far corners of the body and wide tracks, it is set up for superior roadholding.

It also gives the car a long wheelbase which, combined with generous body width, translates to a roomy interior. The boot is also spacious and accessible.

Unfortunately, those large 20-inch wheels, shod with run-flat tyres, are a compromise to ride comfort. Road noise is higher than expected.

On the whole, the car is not as refined as, say, the Lexus NX or the RX. Size-wise, it is closer to the NX, but weight-wise, it is more similar to the bigger RX.

Poorer insulation and ride aside, the car betrays other minor shortfalls, which prevent it from being a strong rival to Lexus' SUVs.

Its Hold function is sticky and requires plenty of throttle input to release. It has a suede-lined centre console and rubber-lined cubby holes, but also plasticky bits and a manual roller cover for a storage compartment fore of the gear lever.

The gear lever has a stylish, sporty design which is similar to what you find in modern Mercs, but has a flimsy tactile feel to it.

Its digital displays lack the sophistication expected of a premium product. In fact, its instrumentation is only partially digital.

Yet, credit must be given to Infiniti for giving the world a new engine technology which holds vast potential. Most other manufacturers are expending resources on cool infotainment systems.

The engine should be a blast in a lighter model with better road dynamics - like the Q60.