THE quality of diesel engines introduced by premium European brands over the past few years is remarkable, changing the way many Australians think about the compression-type engine.

But the idea that a diesel engine could be used to power the most luxurious sedan in the BMW stable is another thing.

Driving the new 730d diesel on a return trip from Sydney to the trendy town of Berry, south of Wollongong, revealed that the engine is indeed worthy of installation in the 7 Series.

BMW has done a lot to stop the traditional diesel clatter from penetrating the cabin, but outside, the diesel rattle is real, although muted like most premium diesels. To stand and listen to a diesel rattle coming from a new $200,000-odd BMW takes some getting used to.

BMW suggested we wouldn’t be able to pick it is a diesel from inside the car, and this is almost correct.

A slightly lumpy idle gives it away. At this end of the market you usually have to look at the tacho to see if a petrol engine is running at idle, but you can feel the diesel ticking over.

In every other respect, it is a great engine, with vast reserves of torque to propel the 7 Series fast enough for all conditions we experienced, usually without exceeding 1500rpm.

Of course, if you plant the foot at 2000rpm or 2500rpm, things start happening more quickly, but it has enough low-down urge not to warrant that too often.

Interestingly, the 730d has a fairly sporty engine note that sounds like a cross between a petrol and diesel engine when opened up. Yet, it is also refined, revving smoothly.

The 730d is at its happiest on rolling hills where it can use its torque to maintain momentum without working up a sweat. This kind of leisurely driving attracts many people to diesel.

The only blemish surfaces when acceleration is required in a hurry, with a slight turbo lag in evidence before the big BMW gets into its stride.

With all that torque on tap, the automatic transmission does not have to work hard, holding a gear instead of hunting for another ratio. When it does shift, it is almost imperceptible.

There are no paddles or buttons on the steering wheel to shift gears, and this is just fine. BMW 730d customers are unlikely to pretend they are in a race car.

If they do, a Sport mode buffs the engine throttle, transmission changes, steering and suspension settings to a sportier feel.

This knocks back the gears until the engine has race-like revs, but luckily, the driver can alter the settings in the car’s computer and, for example, have the engine and throttle set to Normal and the suspension and steering on Sport.

This firms-up the damping and gives the steering a heavier feel while leaving the engine and transmission alone.

Fuel consumption is unlikely to be a key motivator for 7 Series customers, but 730d customers will at least be able to be pre-armed with impressive fuel economy figures if dinner party guests query their choice of such a large vehicle.

The average consumption figure didn’t look great as we sat in Sydney traffic gridlock, moving up to 9.9 litres per 100km, but once moving, things got a lot better.

By the time we reached Berry, the fuel economy average was reading 6.9L/100km.

When we returned to drop the cars in Sydney, the figure has dropped to 6.6L/100km.

The smooth route was eco-friendly, apart from the city start and some spirited curves, but that is still an impressive number for a car weighing 1865kg.

And the car does feel big when tipped into the bends, but nonetheless, involving to drive.

In Sport mode, the steering gives good feedback and is well weighted, while in Normal mode it feels light, in keeping with a luxury vehicle.

The suspension settings can be varied, but the Normal mode seems to work well enough, while the Sport setting is good for settling the body down when you are encountering twisty sections of road.

While the car handles the curves, the wide seats provide less lateral support.

Cabin refinement is excellent, with tyre and engine noise well suppressed. A high degree of wind noise was noticeable around the A-pillar and wing mirror, but that was only in a high-wind area on a windy day.

BMW’s driver head-up display is particularly useful, projecting information such as speed and satellite navigation instructions so the driver can keep the eyes safely forward.

Thankfully, BMW has improved the iDrive control feature which is a dramatic improvement over the first clumsy and confusing system.

The new iDrive is intuitive and most people would be able to navigate through the menus without being familiar with the system.

The interior of the new 7 Series is simple and stylish, lifted by features such as a stitched dashboard.

As you might expect, there is masses of interior space and plenty of leg and head room for the rear passengers.

The rear seats, just like the ones in the front, are comfortable.

In a nod to the past, BMW has also included two cigarette lighters and ash trays to help the rear occupants smoke away to their lungs’ content.

The boot is tall and long but not as wide as you might think as the wheel arches intrude a fair way into the luggage area. Still, there is a lot of room whichever way you look at it.

A handy inclusion is a power-shut boot so you do not waste energy closing the lid.

Styling is of course subjective, but there is little doubt the redesigned 7 Series looks more athletic than the car it replaces. Watching a new 730d pass a previous model 7 Series on the open road demonstrated how fat and heavy the last car looks, especially from behind.

That has been fixed and the new car looks good from the back and the sides.

The front is a different case, as the nose is a mix of the sleek sloping headlights and the upright, large kidney grille.

It doesn’t look as bad as the previous model, but in my mind, is still unconvincing.

Overall, the 730d is an overwhelmingly competent car. Any concerns about the engine performance are unfounded, not only strong but capable of excellent fuel economy.

Given that it is also fairly refined and is the cheapest model in the 7 Series line-up, the 730d makes a compelling case.