The BMW X6 is a cross between a four-door coupe and an SUV. It looks to mix the attractive styling and responsive handling of the former with the raised stance and off-road ability of the latter. Unfortunately it ends up doing neither particularly well - although it's pretty good to drive for an SUV, it falls down when you head off-road. There's better news in the shape of some great diesel engines, which offer impressive performance combined with reasonable few economy. If it's all-out performance you want, then look no further than the crazy M50d version, but our choice would be slightly more sensible xDrive 40d.

BMW X6 buyers have a choice of five engines – two petrols and three diesels. The petrols are fantastic performers, but fuel economy isn't their strong point and they'll be very costly to run as a result. The diesels look like a much better bet, particularly as they offer similar performance to the petrols but are much cleaner and more efficient. The cheapest 30d model goes from 0-62mph in a hot-hatch-like 7.5 seconds – very quick for such a large car. The larger 40d engine takes a full second off that time, while the M50d takes a barely believable 5.3 seconds to do the sprint. And the X6 isn't just fast in a straight line – it's very agile, too. Responsive steering, confidence-inspiring grip and excellent body control combine to deliver a very satisfying driving experience. And BMW's optional Dynamic Performance Control system makes it even better, constantly adjusting the spread of torque across each axle to maximise grip.

This is where your choice of petrol or diesel will make the biggest difference. The 35i petrol engine can only return a paltry 28mpg fuel economy and emits a hefty 236g/km of CO2, so big bill are the order of the day when you fill up or renew your tax. The faster M50d diesel manages more impressive figures of 36.7mpg and 204g/km of CO2. Prepaid servicing packs can take the sting out of maintenance costs for up to five years or 60,000 miles of ownership, however there's no escaping the fact that a high-performance SUV such as the X6 will always be expensive to insure.

Whether you love or hate the BMW X6's looks, you certainly can't describe it as forgettable. Below the waistline, it's styled similarly to its beefy X5 sister model, while higher up, you get rakish coupe lines similar to the 6 Series Gran Coupe. It's an interesting and unusual combination that won't be to all tastes – but those who enjoy turning heads on the road will like it. All versions of the X6 have 19-inch alloy wheels as standard, however you can upgrade to even more imposing 20-inch wheels with the optional Dynamic Package.

Although it looks pretty big from outside, the X6 'Sports Activity Coupe' is strictly a four-seater, with two individual rear seats. Luggage capacity is more impressive: you can get 570 litres into the hatchback boot. There's also discreet secure storage beneath the boot floor. All X6's are well equipped, with xenon headlights, climate control and parking sensors among the wide array of gadgets. The latter item is particularly important given this car's pretty poor rear visibility.

Because it sells in relatively small numbers, the BMW X6 has not yet been crash-tested by Euro NCAP. Other BMW models have done well here, though, so buyers should not be unduly concerned about safety. The X6 packs a long list of standard safety equipment, including no less than 10 airbags, ESP, Isofix child-seat fixtures, tyre pressure monitoring and extra-bright xenon headlights. Most of the X6's drivetrain and other components have been proven elsewhere in the company's range, so reliability should be strong.