At a glance you could easily mistake the BMW X5 M50d for one of its lesser X5 stablemates, but aside from the familiar styling there’s nothing ordinary about the M50d.
Only the set of tractor-sized tyres and the M50d badge on its tailgate suggest something special might be going on under the bonnet.
And it certainly is. The BMW X5 M50d harbours a monster diesel engine that would seem more at home in a Le Mans racer than shoehorned into an entirely practical, family-fit SUV.
It’s an impressive powerhouse, but the nameplate may be a tad confusing. It’s not in fact a 5.0-litre unit as the badge might suggest but instead a 3.0-litre six-cylinder inline diesel with triple turbochargers that makes 280kW of power and a colossal 740Nm of torque.
It also powers the (slightly quicker) BMW X6 M50d we tested in 2012.
BMW asserts it’s the most powerful volume-produced six-cylinder diesel engine in the world – and they’re not inviting argument.
It’s enough grunt to propel the X5 M50d from 0-100km/h in 5.4 seconds flat - seven-tenths behind the X5 M. Top speed is a governed 250km/h.
Developed by BMW’s M GmbH go-fast division, the same group that builds the full-fat M models, the X5 M50d falls under the M Performance brand that includes the X6 M50d and the recently released M135i hot-hatch.
There’s also an M550d and M550d Touring, but unfortunately for Australia these two variants are only available in left-hand-drive with xDrive.
The BMW M Performance line is intended to fit in between regular BMWs and the range-topping M models – much like AMG Package Benzes and S Model Audi’s (that sit below RS versions).
Audi will soon step into the same ring with its upcoming quattro GmbH-prepared SQ5 TDI when it launches in April 2013.
Audi’s high-performance mid-size SUV will get a 230kW/650Nm 3.0-litre twin-turbo diesel, good enough to propel the SQ5 from 0-100 in 5.1 seconds, making it three-tenths quicker than the larger X5 M50d.
There’s a reasonable price leap from the regular X5 to the M Performance version. While the X5 M50d is priced from $146,500 (before on-road costs), it sits comfortably below the full-strength 408kW/680Nm BMW X5 M, which wears an even more daunting $182,700 price tag.
On the cheaper end of the diesel line-up (directly below the M50d) is the 225kW/600Nm BMW xDrive40d Sport model, priced from at a relatively affordable $112,800 before on-road costs.
The M Performance treatment of the X5 M50d is as much about the drivetrain as it is about powertrain development – so along with engine and transmission tuning, the suspension and steering have all been worked on in trademark M division style.
Design mods are clearly less conspicuous on the X5 M50d than they are on the full-blooded X5 M, but the beefed-up wheel arches (front and rear) and tuner-style rear apron housing with black exhaust tips give some indication of its high-performance pedigree.
Further differentiation comes from the side mirror caps and horizontal grille bars in a ferric grey metallic, together with the body-coloured front apron housing side air intakes normally reserved for foglights.
Bar the rear model badge, it’s all quite subtle – perhaps even bordering on sleeper-status. Inside, the M touch is similarly understated, with just a series of small M logos scattered throughout the cabin.
All the important stuff is there, though. The thickly padded M leather steering wheel with paddle shifters and excellent tactility is a favourite. So too are the Alcantara/Nappa leather M sports seats.
They’re well bolstered up to the armpits and the Alcantara inserts are not only comfortable, but will hold you secure no matter how high the G-forces.
Commensurate with its near range-topping position, the X5 M50d comes fully loaded with a stack of features, many of which are optional extras on regular X5s.
Highlights include: bi-xenon headlights with adaptive function and high-beam assist; head-up display; internet functionality; four-zone climate control; navigation with 8.8-inch colour screen and 12GB hard drive; auto-sensing headlamps and wipers; rear view camera with parking sensors (front & rear); and 12-speaker 205-Watt hi-fi system.
One very minor irritation is that despite the keyless entry feature and push button start, you still need to insert the key fob into a slot before hitting the start button.
Despite its luxury status, the X5 M50d’s interior is more business class than first class. The dash and centre stack is all too familiar and found in almost all other BMWs from 1 Series through to 7 Series.
While almost all surfaces are soft touch and have a quality look about them, the cabin is too monochromatic and falls short of the Audi Q7 in this regard.
The BMW X5 M50d is a large SUV, so there’s plenty of room for five adults, although the rear seating design is best suited to two adults, at least for longer trips.
An almost flat floor aids rear seat legroom and there’s a tonne of headroom fore and aft.
Buyers can also option third-row seating with two separate folding seats boasting additional ventilation ($7600), but you will forfeit the space saver for a mobility kit.
The X5 gets huge front door pockets capable of swallowing several large water bottles, but the glove box is small as is the centre console storage bin.
There’s an ample 620 litres of load space in the luggage compartment that increases to 1750-litres with the rear seatbacks folded (not completely flat) and the X5 also gets a split tailgate for easier access.
While the flexibility of this large SUV can’t be discounted, the decision to purchase an M-powered BMW is surely all about the performance. Well, the X5 M50d gets plenty of that.
Fire up the mighty 3.0-litre diesel and there’s no disguising that familiar clatter. It sounds like any other oil-burner at idle, giving no hint of what's to come.
Call it a Jekyll and Hyde shift, but the moment the rev counter nudges 2000rpm, you’ve got a full 740Nm of torque taking care of business. And that clatter has developed into more of a snarl.
There’s almost no lag, either, with the first of the three sequential turbocharges chiming in at speeds just above idle. Push on, even slightly, and the larger second turbo spools up from just 1500rpm and you can feel a deliberate but linear surge.
Leave your right foot planted on the throttle and all three turbocharges are on song – and the X5 M50d moving rapidly, with terrific in-gear acceleration.
Throttle response from almost anywhere in the rev range is exceptional for a vehicle of this size and mass (2150kg), and while maximum power output is between 4000 and 4400rpm this diesel doesn’t mind revving out to 5400rpm.
Fuel consumption is rated at just 7.5L/100km, too, with our broad range of speeds and roads during a rain-drenched test period bringing 10.8L/100km up on the trip computer.
The X5 M50d gets a slick-shifting eight-speed automatic transmission that’s been fettled by the M-division squad and you’ll be hard pressed picking it from a dual-clutch unit, such is the shift speed.
The gearshifts themselves are totally seamless – you’re aware of them, but you can’t feel the transition from one gear to another even when you’re going for it.
For extra driver involvement the BMW X5 M50d offers M mode, which holds the gear ratios until the engine revs hit the limiter.
The X5 M50d’s grip levels are astonishing, particularly in the mostly monsoon conditions we had to endure during our test.
With massive Dunlop Sport 315/35/R20 series tyres down back and 275/40/R20s at the front, there’s plenty of contact with Terra Firma. And even during full throttle launches from standstill we couldn’t detect any slip or loss of traction. Traction control was certainly working (you could see it light up in the dial), but was so subtle as not be felt.
The BMW X5 M50d is equally adept in the corners, featuring M-specification tuning of the chassis. Body roll has virtually been eliminated and composure is rock solid – even in slippery conditions.
While there’s decent steering accuracy through the corners and it’s nicely weighted from the dead centre, the level of driver feedback isn’t a match for the benchmark steering of the rival Porsche Cayenne.
And despite featuring air suspension and automatic self-levelling at the rear axle, the X5 M50d offers a ride that is, perhaps expectedly for its performance slant, on the firm side.
Small imperfections on the road are felt through the cabin, though larger bumps are absorbed quite well given its stiffened chassis set-up.
The BMW X5 has consistently been one of the best SUVs to drive, and the BMW X5 M50d variant is a worthy addition that offers buyers a chance to taste the world of M performance for less than $150,000 and without spending excessively on fuel.