The transmission can be run in one of two main ways. Auto eDrive mode defaults to using the battery for forward motion at low and moderate speeds. BMW says this will ensure ‘emission-free’ travel in built-up areas. At higher speeds, motive power is shuttled between the petrol engine and battery, though the engine sparks into full-time use at around 50mph or if the driver hits the accelerator’s kickdown point.
The Max eDrive mode ensures that the car runs purely on battery power until speed reaches 50mph, while a Battery Control setting allows the driver to decide how much battery power to reserve for later in a trip, allowing for, say, emission-free driving when entering a city after a motorway journey.
In addition there are three adaptive chassis settings, which also affect the way the hybrid transmission works. Comfort mode is intended to deliver a smoothly balanced combination of battery and engine use and the most relaxing suspension settings. Sport mode sees the electric motor and petrol engine work together to give more outright performance as well providing sharper throttle and steering responses and stiffer suspension.
Eco Pro mode is designed to maximise the car’s electric range, and to this end it features a special energy recuperation function to help recharge the battery when driving. Between 25mph and 99mph, a coasting function kicks in when the driver lifts off the accelerator. At this point the petrol engine switches off and the electric motor in the gearbox is turned by the car’s wheels as it coasts along. This means the electric motor can act like an old-style bicycle dynamo, generating electricity and charging the battery.
Both the heating and air conditioning systems can be run electrically from the lithium ion battery pack, which also allows the cabin to be ‘pre-conditioned’ by remote control.
What's it like?
Vast. This long-wheelbase version is more than 5.2m long and rear cabin space is very impressive. The front of the cabin is equally accommodating and the interior design theme - which is far more button-heavy than that of the arguably more futuristic Mercedes-Benz S-Class - is a matter of taste. But you could hardly argue with the fit, finish and sense of luxury.
The distinct downside of this car as a top-end luxury model is the size of the boot, especially when compared to the size of the cabin. Its volume is gained more from its depth than from the loading height, and four full-size suitcases look like they’d be a very tight fit.
Depending on which of the numerous powertrain management options has been selected, the 7 Series hums away from standstill in electric drive. It doesn’t take much demand for speed from the driver for the engine to kick in, but the car is also - via the sat-nav - ‘aware’ of where it is, so the petrol engine does the majority of work when the car is out of town or on the motorway.
Air suspension on both the front and rear axles ensures that this 7 Series does a very impressive job of isolating its occupants from the outside world. But this car’s ability to shake off poor roads, along with its exceptional stability when indulging in masterful full-bore, twin-engine overtakes, must be credited to the stiffness and stability of the body structure.
It’s a remarkably clever mix of materials. At its base are various grades of steel, to which BMW has added carbonfibre reinforcement in the arc of the roof, in the B-pillars, over the centre tunnel and for the rear bulkhead. Giant aluminium castings are used for the front suspension towers and the crash legs. There’s no doubt that this composite structure is the key element in making the 740Le move with such assurance and poise. On top of that, the XDrive all-wheel drive system is permanently engaged, rather than working on-demand, which only adds further surefootedness.
The only other real issue with the 740Le drivetrain is the noise from the petrol engine under acceleration. While active engine mounts do a good job of isolating it from the cabin, it sounds pretty harsh until the growling exhaust note cuts in above about 3500rpm. BMW sources say the harshness is an inevitable function of the engine’s high specific output.
Should I buy one?
This is about as niche a vehicle as you can get. Are you a successful business tycoon who wants to get ahead of forthcoming emissions legislation by being able to drive around a city centre on battery power while not sacrificing super-luxury and blistering back-road performance? Not likely to be on a regular airport run with a boot full of Samsonites? It’s perfect, then.
BMW 740Le xDrive
Location Munich; On sale Now; Price £74,880; Engine 4 cyls, 1998cc, twin-turbo, petrol, plus electric motor; System power 322bhp; System Torque 369lb ft; Gearbox 8-spd automatic; Kerb weight 2000kg; 0-62mph 5.3sec; Top speed 155mph (87mph in EV mode); Economy 134mpg (combined), 28 miles EV range; CO2 rating/tax band 49g/km, 11%