We like
Great engine response and refinement, low fuel consumption, excellent fuel range, small weight penalty, the sportiest diesel luxury car currently available by far

Room for improvement
Doesn't feel as wieldy as 530i, active steering takes some getting used to, run-flat tyres return choppy ride, $2000 premium over 530i sedan

To D or not to D - that is the question.

With apologies to W. Shakespeare, BMW's 530d takes a seat alongside Mercedes-Benz and Audi in offering a diesel engine option in the $100,000 (plus) luxury sector in Australia.

And why not, since diesel sales are up 60 per cent overall this year, fuelled by surging petrol prices, a greater variety of models available, and the realisation by many Australians that this form of engine technology has come in leaps and bounds in recent years.

There is also a 120d, as well as a 320d, in BMW's diesel-powered passenger car range, supported by X3 and X5 3.0d SUV alternatives.

Diesels are the new black this season, then.

But be prepared to fight for your right to save fuel. There is a price to pay for the greater parsimony diesels bring - and it's a philosophical as well as a monetary cost.

If you want the sportiest and most involving diesel sedan available, then step forward BMW, because the 530d will outpoint and out-excite (if not out-cling, since Audi's quattro drivetrain lurks underneath the A6 3.0 TDI) all others of its ilk.

Armed with unflappable poise and huge amounts of body control, the 530d is the only luxo liner that really is finely tuned to the keen driver's desires.

Like every other E60 5 Series, the 'd' will tear into a series of tight bends, or bobsled through a wide arc of a corner, with slick ability and sweat-free ease, like the BMW it undeniably is.

But 'd' isn't quite as athletic as the lighter, lither 'i' 530 petrol-powered protagonist, which zigs and zags like nothing with four doors and a big boot.

With the diesel you're conscious of the 90kg extra weight - mostly plonked ahead of you - blunting ever-so-slightly this BMW's dynamic balance.

And, as with the rest of the 5 Series range in Australia, the standard "Active Steering" - which changes the ratio of the steering rack according to the speed you're travelling - takes time to acclimatise.

It's just that, in the 530d, this might take a little longer than usual. Could it be the added kilos? Whatever it is the steering feels even more unnatural.

This seems to manifest itself in more clipped curbs and corners at low speeds after a period of high-speed manoeuvres. It's as if your muscles and mind seem to 'remember' and thus subconsciously dial in the amount of force needed to turn the wheel.

Never mind. As we said at the car's launch last year, the 530d suspension's ability to sit the sedan squat over all manner of road conditions and surfaces is frankly second-to-none.

The controversial 'Run-Flat' tyres, with their harder sidewall compounds, contribute to an annoyingly busy ride, but beyond this the suspension deals with ruts and bumps with rock-solid stability and exceptional finesse, particularly at very high speed.

So the 530d, though still brilliantly balanced, isn't quite the best handling 5 Series you can buy.

Moving on, the Bavarians are also renown for making magnificent six-cylinder motors. And the BMW unit is probably the best diesel around.

With 160kW of power available on tap at 4000rpm and a sub-supercar 480Nm of torque cascading from as low as 1750rpm to just 2750rpm, the pulling properties of this particular powerplant are persuasive, in more ways that one.

After a slight hesitation, the 530d thrusts forward with towering force, building up momentum without undue effort.

In fact, the mid-range wallop adds a uniquely un-BMW source of entertainment, since it doesn't need high revs before starting to deliver.

Plant the foot from 60km/h and the forward thrust is deliciously intoxicating. The diesel just doesn't let up while a 530i won't be able to keep up. And check the tacho: the engine is barely turning over 1400rpm at 100km/h.

In the meantime the absolutely superb ZF six-speed automatic is like the diesel engine's conductor, orchestrating the perfect spread of ratios for the engine to revel in.

Select 'DS' (Drive Sport) mode and the engine's responses are quite startling indeed.

For the record, the torque top is 180Nm more than the N52 B30 3.0-litre petrol unit found in the spoilsport 530i. And the official 0-100km/h-sprint time of 7.2 seconds is amazing when the petrol car does it in 6.7.

Plus, from the driver's seat, you're only hazily aware of the diesel din that for decades has discouraged buyers, because BMW has done a bang-up job caning the clang - even at start-up.

Best of all though, the 7.5L/100km on the official average cycle (compared to the petrol's 9.3 we averaged 7.5 driving the diesel very hard indeed on country roads and 9.5 in heavy city traffic) is fantastic frugality for the performance on offer.

No matter how you look at it, all the figures are outstanding for a diesel.

But, like the dynamics, it isn't the best BMW can do (fuel economy excepted of course), if what you really really want is classic BMW engine characteristics.

The 2006 530i recently tested revved to the right of its dial like a Geiger counter going off at Chernobyl, playing its mellifluous mechanical melody like it was performing in the finals of Motor Idol.

Anyway, real or imagined, that's the BMW engine fantasy that people buy into the BMW legend for, and the 530d - no surprise here - just doesn't deliver as beautifully as its 530i sibling.

You get the idea then - the diesel is really a very different sort of BMW 5 Series. But the rest of the car is exactly the same as in the petrol version.

To recap, this means a modern and driver-dedicated cabin featuring a dashboard with instrumentation that rate as among the simplest and most effective available.

Few sedans have the driving position as sorted as the E60, backed up by beautifully comfortable seating for four (the rear centre pew is punishment), excellent space up-front and tolerable room for adults out back, backed up by sound ergonomics, a real feeling of cocooned safety and security, and too much plastic trim.

The ever-divisive i-Drive controller - brilliantly flawed in its execution, sometimes allowing unparalleled access to secondary functions in one action and then too damn fiddly and distracting for other operations the next - is great simply because it pushes packaging and technological boundaries.

Speaking of which, in the 530d test car, BMW jam-packed it with some interesting and/or novel options that ballooned its price to well-beyond its $114,500, while giving us the opportunity to assess what they're like to live with.

By far the best one is the $4500 'Active Cruise Control' function, that uses sophisticated radar to alter your set cruising speed according to the vehicle ahead, while reacting far-faster than a human can if instantaneous braking is required.

Nobody could argue that the $2600 head-up display, that reflects various speed and other vehicular-related information on the lower part of the windscreen directly ahead of you, is effective in reducing the times a driver needs to take his/her eyes off the road. But why does BMW charge so much for it?

On the other hand the $4000 Voice Recognition device, which activates various features and controls after you've pressed a button to 'ask' the car for them, is a frankly annoying and slow-witted gimmick.

The mental drain that results after its inevitably botched attempts to carry out even the simplest command far exceeds any physical or time toll taken by simply doing it yourself.

As it is packaged with BMW's effective bird's-eye satellite navigation and TV prep however, some of the sting is taken out of that seemingly extortionate price.

But these are all beside the point when assessing the 530d.

If you want the ultimate diesel driver's car then look no further than the BMW. It has the firm's dynamic DNA infused throughout.

But if you demand the best BMW 5 Series this side of an M5 then you can save your $2000, keep collecting those forever-expiring discount petrol coupons, and pick the 530i, which remains one of the compelling sedans on this planet.

So the 530d is a great diesel and a very good BMW.

To Bimmer or not to Bimmer... that is the real question here.