BMW Australia has introduced its most affordable 7 Series, which is also the most efficient.

The 730d is the first diesel version of the range-topping limousine to be sold in Australia, arriving with a sticker price of $198,800 – $4200 less than the petrol six 740i.

While it might be new to Australia, BMW has sold a diesel 7 Series in Europe since 1996 where tax regimes encouraged the take up of diesel in all vehicle classes, including luxury saloons.

The price advantage is likely to put the 730d on buyer’s radar, but it is the efficiency of the engine that BMW is keen to promote.

The 730d has an official fuel consumption figure 7.2 litres per 100km – superior to any of its rivals, including the Mercedes-Benz S320 CDI (7.8L/100km), Audi A8 3.0 TDI LWB (7.9 L/100km) and Lexus LS 600hL petrol electric hybrid (9.3L/100km).

While reducing the fuel bill is not a priority for most 7-Series customers, the low emissions of the 730d could be a selling point.

Using the official ADR cycle, it emits just 192g/km of CO2 and is the only car in its class to dip below the 200g/km mark.

This compares favourably with its rivals, including the Mercedes S 320 with 202g/km, the Audi A8 with 224g/km and the Lexus LS with 219g/km.

The BMW is not the class leader when it comes to acceleration though that honour goes to the Lexus with a 0-100km/h sprint of 6.3 seconds.

As for the 730d, 7.2 (the same figure as its fuel consumption) pops up on the stopwatch after the 0-100km/h run.

That is still good enough to beat the Mercedes S320 which runs from 0-100km/h in 7.8 seconds, while the Audi does it in 7.9 seconds.

The 730d is powered by a 3.0-litre in-line turbo diesel six-cylinder using third-generation common-rail direct injection which puts the fuel under 1800 bar of pressure.

It uses a variable geometry turbocharger and has an aluminium block to keep the weight down.

It produces a healthy 180kW of power at 4000rpm, but its real strength comes in the form of torque as it manages to produce 540Nm from 1750rpm all the way through to 3000rpm.

The same engine will be fitted to the 3 Series in the form of the 330d which goes on sale in Australia next month.

The 730d is available with one transmission – a traditional six-speed automatic that transfers drive to the rear wheels.

While the 730d is a full-size luxury sedan, it is not an overly heavy vehicle, tipping the scales at 1865kg.

That is a respectable 55kg less than the previous 7 Series diesel in Europe, and is aided by lightweight aluminium being used for the doors, bonnet, roof and rear axle. It is just 5kg heavier than the six-cylinder 740i.

While it takes on the role of the entry-level model, the 730d has the same equipment level as the 740i. From a mechanical perspective that means the 730d sits on 18-inch wheels and runs the same suspension system with variable damper control on each wheel in response to road surface conditions.

The driver can also pick from three suspension settings including Comfort, Normal and Sport.

Like its 7 Series siblings, the 730d uses the new double-wishbone front suspension and V axle multi-link rear suspension, much of which is aluminium.

It has hydraulic-assisted steering that uses variable-gear steering assistance requiring less input at low speeds, and the rear wheels can also steer slightly depending on speed.

The 730d comes with a high level of technology, including standard head-up display to project information such as speed and satellite navigation details on the windscreen just above the dashboard.

There is also a rear vision camera, adaptive headlights, TV tuner, voice control for many of the functions and Bluetooth preparation.

The 730d also comes with four-zone climate control, a sunroof and a sound system with six-CD changer and a USB audio interface.

Leather seats are standard and the front seats have a heating function.

The doors are fitted with a standard ‘soft close’ system which means the occupants don’t need to shut the door completely – it will do it for you.

Unlike one of its competitors, the 730d has standard metallic paint.

Optional systems include the thermal imaging-based night vision that now has a pedestrian warning function as well a camera based system that helps with side vision during the day.

The side view system uses cameras in the front wheel arches to give the driver a better view of passing traffic when attempting to pull out of places such as side streets.

Another option is the lane-change warning system that detects cars in the blind spot and issues a warning during lane changes.

BMW says the 7 Series is also the first car to contain its entire driver’s handbook on its computer system, viewed through the centre screen on the dashboard.

Like all 7 Series models, the 730d features some interesting fuel-saving technology.

Flaps in the radiator grille brake cooling ducts shut when not required to increase aerodynamic efficiency.

The 730d’s alternator only diverts power to the battery when the engine is off throttle and when the brakes are being applied.

BMW Australia won’t be drawn on how many 730ds it expects to sell, but says it doesn’t expect the car to be a niche player.

It is confident 7 Series customers will be open to the idea of driving a vehicle with a diesel engine, as many have been exposed to quality diesel engines in BMW products such as the X5.

BMW Australia points out that more than a third of all the cars it sells are fitted with diesel engines, although a large proportion of those are the X5 and X3 SUVs rather than passenger cars.

However, in the 5 Series, the 520d diesel is both the most affordable and most popular.