It is hard to beat the 730d in BMW's 7-series. It's agile and frugal ... a real über-saloon

The BMW 7-series is the car that, in its previous incarnation, brought iDrive to the motoring world. Designed specifically to bamboozle anyone over 40, iDrive replaced many switches and buttons with a single large knob which could be turned, pressed and nudged sideways to achieve in maybe seven moves (your eyes glued to the screen all the while), what could previously be done in one or two.

If you've ever tried to alter the bass response of an early iDrive-controlled stereo system, you'll know what I mean.

There were niceties, though. The knob was haptic: its feel altered according to what it was being asked to do. As a piece of electromechanical engineering it was delightful. But most people cursed it, while simultaneously grimacing at the severe detailing and anti-beautiful sculpting of the 7-series itself.

Against my instincts I grew to like the look, especially if the 7-series being looked at was painted black and was the mildly facelifted version. It had menace, mystery, assertiveness. And provided my daughter was aboard to drive the iDrive, we got along fine. Much better than on the original launch of the previous 7, anyway, when I had to enlist the aid of a BMW person just to get the thing started and moving. After which the indicators never seemed to do what I wanted and I got in a terrible muddle with the gear selector.

The profile of this new 7-series is again squared-off with a bluff nose, but this time the nose contains the biggest pair of grille nostrils yet seen on a BMW. The headlamps have that stern, eyebrowed look again, while the flanks have a large depression formed just behind the front wheels, where there's also a bright-metal badge straddling front wing and door as though it were some sort of hinge.

The stereo system even has built into it the Gracenote database of album tracks (the one that identifies CD tracks when you load them into iTunes), so it knows and stores the names of your CDs' contents.

Inside, the iDrive button has shrunk and is surrounded by other buttons by which you can take shortcuts to your desired function. What has happened, in fact, is that the pioneering iDrive has morphed into something resembling Audi's Multi-Media Interface, and therefore is now usable by normal people.

The cabin is more cohesive-looking than before, and can feature particularly handsome wood trim which, far from being mere garnish, performs structural functions such as forming the door-pulls. There is, as before, a long-wheelbase version with huge rear legroom.

No longer does the top 750i version have a profligate V12 engine: it's now a 4.4-litre twin-turbo V8 with the turbochargers neatly placed in the centre of the vee. It is more economical yet 41bhp more powerful, making 407bhp. Then there's the 740i which is also downsized, this time from a V8 to a 3.0-litre, twin-turbo straight-six with 326bhp.

Finally comes the 730d, alone in having an engine capacity still properly related to the model name. It's still a 3.0-litre turbodiesel as before, but currently producing 245 bhp. This will be far and away the biggest seller, not least because it produces under 200g/km of CO2. No other plutocratic saloon is as frugal, not even the much-vaunted Lexus LS 600h hybrid.ix-speed automatic, rear-wheel drive. The performance of the 730d offers 152mph, 0-62 in 7.2sec and 39.2mpg official average. Priced at £54,160 it has a six-speed automatic rear-wheel drive.

You can have a driving dynamics package which includes steering that is able to speed its response at low speeds, automatically keep the car level (-ish) when cornering and apply small amounts of steering to the rear wheels when cornering or manoeuvring.

I drove a long-wheelbase 750iL so equipped, which proved fast and quiet but still felt a hefty handful despite its front-mounted cameras designed to reveal, on a split left-right screen, what lies below your sightline up front. This is one bulky car. Its suspension wasn't as supple as it should be, either, especially for those being chauffeured in the back.

The 730d, however, felt as a BMW should feel. Devoid of chassis-dynamics cleverness it proved keen, agile and engaging, with nearly as much real-world pace as the 750iL. This is the 7-series of choice, just as it was last time around. Seems that the cheapest and greenest BMW über-saloon is also the best.

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