BETTER performance is one thing that the existing X5 diesel doesn’t really need. But this hasn’t stopped BMW installing a new twin-turbo diesel option in its sporty luxury SUV, to create a compelling alternative to the continuing 3.0d version. However, the real attraction of this new X5 3.0sd is its quite incredible efficiency, since the significant gains in power and torque come at minute increases in the official fuel consumption and CO2 emission ratings. So if you’re going to buy an X5 and can foot the $6500 premium BMW charges for an extra turbo on the equivalently-equipped 3.0d Executive, then that extra ‘s’ will certainly satisfy.