BMW X5 news - Emission statement - 2008

Thus far, BMW has tackled the emissions-reduction game by investing in efficient, turbocharged diesel engines, stop-start technology and brake energy regeneration instead of hybrid systems.

But at this year's Geneva show, BMW will bung the whole lot together in a seriously clever X5 concept designed to show off its green credentials and, no doubt, stick it in the eye of the anti-4x4 crowd.

So how do you create an X5 that returns 43.5mpg and 172g/km of CO2 while still hitting 60mph in under nine seconds? Erm, not easily.

BMW has started with its stunning two-litre, twin-turbo diesel engine - as seen in the 123d - which develops 201bhp and 295lb ft of torque. The unit is mated to a dinky electric motor that delivers an extra 20bhp and 155lb ft of torque under acceleration.

This electric motor is powered by lithium ion batteries stored in the boot, which are charged through a combination of energy produced by the generator under braking and on the overrun, and from solar panels mounted on the roof. Told you it was complicated.

That's not quite it for the technological trickery, though. The X5 concept also features BMW's new eight-speed automatic gearbox - due to make its first production appearance in the new 7-Series this autumn - which, say engineers, improves fuel consumption and reduces emissions.

And, last, those turbine-style alloys reduce wind resistance, lessening the load on the X5's powertrain. Not by much, mind - BMW says that at speeds of 100mph, they save 1bhp over conventional wheels. Still, it all counts.

BMW reckons all of the technology showcased in the X5 concept is production-feasible, which means we could see a hybrid X5 or X6 in the not-too-distant future. Blurred decals over the doors will be optional extras, we hear.