BMW has further refined its diesel car line-up in Australia by installing the now-familiar third-generation 2.0-litre common-rail direct-injection turbo-diesel engine into the 3 Series range.

Priced from $56,700, the new BMW 320d is no more expensive than the previous less-powerful version, meaning it is still $3100 more than the equivalent 320i petrol-engined model.

The four-cylinder 320d engine – as recently installed into the 120d, 520d and X3 2.0d – produces 125kW of power at 4000rpm and 340Nm of torque at 1750rpm, making it 10kW and 10Nm more powerful than the superseded 2.0-litre diesel.

It is also 20kg lighter than the previous engine thanks to all-aluminium construction.

Employing variable nozzle turbine technology to broaden the power delivery across a wider rev range, the new engine propels the 320d from rest to 100km/h in 8.2 seconds, which is some 0.6 seconds faster than previous model.

Fitted with a standard six-speed automatic transmission, the 320d’s combined cycle consumption figure is just six litres per 100 km, an improvement of 0.6L/100km or about 10 per cent.

For the record, the 3 Series diesel is 10kW more powerful, has a whopping 140Nm more torque and uses 1.9L/100km less fuel than the equivalent 2.0-litre petrol-engined model.

The 320d is identically equipped to the 320i, meaning it comes standard with ABS, stability control, cruise control, dual-zone climate control, front and rear head airbags, front side airbags, rear parking sensors, rain sensors, one-touch electric windows, seat height adjustment, steering column height and reach adjustment, multi-function steering wheel and run-flat tyres on steel wheels.

For an extra $4800, buyers can choose the Executive model and get alloy wheels, upgraded trim, leather upholstery, partial electric seat adjustment and foglights.

The 320d comes with BMW’s relatively new ‘Incorrect Fuelling Protection System’, which was quietly introduced in March last year to all diesel-engined BMWs sold in Australia.

It is designed to prevent drivers from mistakenly filling their diesel-engined vehicles with unleaded petrol, which will ruin the engine. Incredibly, the Automobile Association in the UK reports that 150,000 cases of misfuelling are reported each year in that country alone.

BMW’s IFPS involved redesigning the filler neck with two opposing contact patches that can only be activated by the larger-diameter diesel pump nozzle. This simultaneous contact releases a locking system that allows the nozzle to engage and pump diesel fuel into the tank.

The smaller-diameter petrol nozzle is not able to touch both contact patches, preventing petrol from being pumped into the tank.