With sufficient charge held by the battery, the petrol engine remains idled. Draw the gear selector back, release the brake and with a gentle nudge of the throttle the X6 gracefully glides away, with only the rumble of the broad tyres providing any interruption to the otherwise eerie silence that you’ll get up to 37mph or a maximum distance of 1.6 miles.
It isn’t until the electrical charge of the battery is reduced, or you floor it with your right foot, that the petrol engine and the second of the electric motors are introduced into proceedings to boost performance.
Between the traffic lights along Miami’s ocean-front roads, where we tested the car, the ActiveHybrid X6 glided along in a hushed and unflappable manner, switching in and out of electric drive with impeccable efficiency.
At greater speed out along on Interstate 95, the introduction of the petrol engine on a continuous basis provided effortless in-gear performance at remarkably low revs, together with highly impressive levels of mechanical refinement.
BMW puts overall fuel consumption at 28.5mpg, but even on light throttle loads we had difficulty getting anywhere near it. The real-world figure, it seems, is somewhere closer to 22mpg, which sounds okay until you consider that the X6 xDrive35d sold
in the UK is capable of 34mpg.
The hybrid architecture adds roughly 250kg to the kerb weight, taking it to a considerable 2450kg. However, the gain is all but offset by the extra reserves brought on by the electric drive, resulting in a
power-to-weight ratio of 198bhp per tonne.
Although the claimed 0-62mph time of 5.6sec is fractionally slower than that of the X6 xDrive50i (5.4sec), subjectively the performance-enhancing qualities of the ActiveHybrid X6’s complex drive system are obvious in other ways.
The way this car can be made to haul away from the lights is nothing short of sensational. In-gear responses are also incredibly sharp, thanks to the ability of electric motors to deliver vast amounts of torque as soon as they are introduced.
Should I buy one?
The great thing about BMW’s hybrid technology is that it doesn’t significantly alter the character of the car in which it has been placed. The addition of electric drive only serves to enhance these qualities even further while providing the basis for improved fuel consumption and lower emissions. The problem is you can’t buy one in the UK, even if you wanted to.