The longitudinally mounted in-line six-cylinder is mated to a standard eight-speed Tiptronic automatic gearbox and, like all new X4 models, a fully variable four-wheel drive system to provide the most potent of the new diesel X4 models with a claimed 0-62mph time of 4.9sec and limited 155mph top speed, in combination with claimed fuel consumption of 47.9mpg and average CO2 emissions of 173g/km on the NEDC cycle.
Performance is defined by the heady levels of torque concentrated in the bottom half of the rev range rather than top-end power. Despite its 1895kg kerb weight, both step off and in-gear acceleration are particularly strong, although it is the hushed constant throttle operation and effortless cruising qualities in taller gears at typical motorway speeds that impressed us most about the top-of-the-line X4 during our first drive in the US. The standard eight-speed automatic gearbox is also terrifically smooth and quick to engage — both on upshifts and downshifts.
The racy qualities of the M40d fully befit the positioning of the new X4, which has moved further upmarket in both looks and features, making way further down the range for the recently introduced X2.
Predictably, given the growth of the latest X3 on which is it based and assembled alongside at BMW’s Spartanburg factory in the US, the 2018 model is larger than before; length is up by 81mm to 4752mm, width has increased by 37mm to 1918mm, height is reduced by 3mm to 1621mm due to lower ground clearance and the wheelbase has been extended by 54mm to 2864mm.
Inside, there’s a familiar-looking dashboard from the X3, featuring suitably high-quality materials, clear and easily read digital instruments, supportive front seats and the sixth-generation version of BMW’s iDrive controller with touchscreen control for infotainment.
The fundamentals are excellent; the driving position is lower and more sporting than that of the X3, the controls are logically laid out, and while visibility to the rear is restricted by the tapered design of the roof, it is supported by highly precise sensors with both acoustic and visual warning as standard. The M40d also benefits from an added range of M Sport touches, including a thick-grip steering wheel, upgraded seats and other niceties.
Accommodation up front is on par with that of the X3, so there’s plenty of head and shoulder room. In the rear, the seats are mounted quite low, but there’s noticeably more leg and head room than in the previous X4, so that should make this car more suitable as an everyday family car.
The automatically operated one-piece tailgate opens to reveal a wide but relatively high-mounted luggage compartment. It boasts 25 litres more than before with a nominal capacity of 525 litres, or 1430 litres when the standard 40/20/40 split rear seats are folded flat.
Does the X4 do enough to elevate itself above the X3?
There’s no doubt about it; the new X4 is a more engaging and rounded car than its predecessor, be it tooling around town or pushing along on the open road. The adoption of BMW’s CLAR (cluster architecture) platform, and with it a thoroughly re-engineered front end featuring a new double-wishbone suspension and claimed 50:50 front-to-rear weight distribution, has brought greater levels of response to the steering, improved body control and a far more settled feel to its ride.
These improved on-road characteristics combine with the traction provided by the X4’s reconfigured four-wheel drive system, which uses a planetary gearset incorporated within the rear axle to juggle drive between each individual rear wheel, to provide outstanding handling. For such a heavy and high-riding car, it can be coaxed to carry high speeds through corners without any undue tyre-squealing drama.