Driven: Infiniti M35h

We check out the 'fastest hybrid in the world' (really)

'Hybrid' is a bit of a dirty word on PH. And for a website that's dedicated to matters pertaining to performance cars, that is perhaps only right and proper. After all, apart from the 911 hybrid racer, and with the arguable exception of the Honda CR-Z, nobody has even tried particularly hard to make a sporty hybrid.

Which is why the car you see here, which weighs fully 1830kg and manages 0-60mph in a healthy-but-hardly-earth-shattering 5.5secs, basks in the glow of being the 'world's fastest-accelerating hybrid'.

But however cynical we may be about its achievements, at least the 359bhp Infiniti M35h doesn't play too heavily on the holier-than-thou eco argument peddled by so many petrol-electric cars, whether they're hair-shirt Priuses or Porsche Cayennes pretending to be a wee bit greener.

No, although Infiniti is keen to point out its eco-cred, with talk of 40mpg motoring, the fact that it can run at up to 50mph in electric-only mode (both true and impressive), and that it emits a mere 162g/km of CO2, this is an electric motor that bends quite a lot of its thoughts towards performance rather than fuel consumption.

And it really does go. The low-down shove of the electric motor (199lb ft at 1770rpm) starts proceedings off, while at higher (petrol) engine speeds the 258lb ft of torque keeps the big M35h surging forward - as an overtaking tool it's rather an effective machine.

The interior is also a step up in terms of quality. The swoopy design is perhaps a bit early-90s-concept-car for some tastes but, provided you like its extrovert nature, it is a fine place to be, with genuinely impressive-quality materials put together in a genuinely impressive way.

The transmission makes a commendable fist of normal behaviour, too, especially considering its trick nature. There are two clutches at work, the first (dry) clutch installed between the V6 and the electric motor/transmission. Electronically controlled, it allows the full decoupling of the V6 when the car is in electric drive and power regeneration modes.

The second (wet) clutch is sited on the other side of the electric motor. It is packaged within the transmission where its function replaces that of a conventional torque converter, in effect turning the 7-speed gearbox into an automated manual - with a cut in fuel consumption of up to 10 per cent over an equivalent torque converter automatic. It's all very clever, and actually quite effective - the changes are smooth and intuitive, and most of the time you wouldn't actually know you're not driving a car with an utterly conventional automatic gearbox.

There is also other clever energy-saving trickery at work apart from just the gearbox. The electro-hydraulic power steering system, for example, only cuts in when steering effort is required, while the brake pistons are actually part-controlled by the electric drive motor.

It's all damn smart, and it makes - potentially - the Infiniti M35h into an effective rival for the likes of the BMW 535d. Especially if you can't bear to fill your car up with the 'd' word. But while the M35h gets close to the diesel BMW in both performance and official economy figures (its 5.5sec 0-62mph sprint is 0.2secs better than the BMW can muster, although at 40.4mpg combined it falls 5.9mpg shy of the Bee-Em), it manages it with a certain amount of compromise.

You see, while BMW has been practising the art ofthe fast diesel executive car for decades now, Infiniti is only just getting going with this hybrid lark. As a result, the whole doesn't quite hang together properly. Occasionally you'll get a jerk from the drivetrain as the engine cuts out or kicks in, or the transmission gets itself momentarily confused. The steering, too, has a momentary lapse occasionally when you catch its power assistance napping. And when you're braking, you'll find that the clever braking trickery actually makes it hard to modulate the pedal.

There's no doubt that the M35h has great potential, but it feels like a product that could yet do with a little refining. If you want the latest in plush eco-tech, or if you want the fastest-accelerating hybrid in the world, then look no further than this car. But if you want a thoroughly polished, fast, efficient executive car, we'd wait a few years yet. Or buy a 535d.

HYBRID VS DIESEL :

Infiniti BMW 5 Jaguar Mercedes

Model M35h 535d XF 3.0 S 350 CDI

Engine V6 hybrid Inline 6 diesel V6 diesel V6 diesel

Maximum power 364 PS 303 PS 279 PS 265 PS

0-100 km/h 5.5sec 5.7sec 6.4sec 6.2sec

NEDC combined fuel 7.0 l/100km 6.1 l/100km 7.15 l/100km 6.2 l/100km

NEDC urban fuel 9.2 l/100km 7.9 l/100km 9.4 l/100km 7.9 l/100km

NEDC extra urban fuel 5.7 l/100km 5.1 l/100km 5.5 l/100km 5.2 l/100km

CO₂ emissions 162g/km 162g/km 169g/km 162g/km

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