Road Test: BMW X5 sDrive25d M Sport 5dr Auto

It had to happen sooner or later. The large SUV, that last bastion of permanent 4WD, where cars are meant to be tough and all-terrain capable, has got its first 2WD-only member - the BMW X5 sDrive 25d. Which is fitting in a way, given that mud-plugging has never been the X5's particular forte.

Because it's a BMW, it's a rear-drive set-up, with another first for an X5 - a 4cyl engine. The 2.0 diesel is the excellent motor from the 325d, with 215bhp and 332lb ft. And due to the weight saving from the deletion of the 4WD system and the smaller engine - the sDrive is 45kg lighter - this M Sport X5 manages 49.8mpg and 151g/km. Impressive figures, and you can drop them even further by opting for the SE trim with smaller wheels.

It's a great engine - smooth, refined and with enough punch for speeds below 50mph, quiet at a steady throttle. A good cruiser. But unfortunately, in something as unaerodynamic and heavy as an X5 - it still weighs nearly two tonnes - it struggles at higher speeds. If you want to slip past another car doing 55mph, the 25d struggles and needs thrashing. Something like the 30d will make less of a meal of it. And by clobbering the 25d, you're not making the most of the engine's parsimony - we got an average of 35mpg while the car was with us, a figure you'd hope to manage with the 30d.

Still, at least you don't really notice the lack of 4WD. Because all the power is sent to the rear wheels, the fronts never scrabble for grip out of tight corners, and on tarmac it's tricky to tell it's not 4WD. It's just like any other X5.

All of which is lovely, but by being just like any other X5, the sDrive doesn't address any of the wider X5 issues - namely, that it's not that good to drive. BMW seems to have forgotten that this is meant to be a Sports Utility Vehicle.

It all adds up to a disappointment. It's impressive that BMW has had the gumption to launch a two-wheel-drive X5, but if we really had to pick an X5, we'd still go for the 30d. The straight-six is simply too good.