A few years ago it would have seemed inconceivable in Australia. Anyone within BMW who suggested the importation of a smart little convertible with a diesel engine would have been given notice on the spot.

Yet we have spent the past week swanning around our home territory on the Gold Coast in just such a car. Top down, late autumn sun pouring into the cabin, smiles on our faces and thinking, ‘Life doesn't get any better than this!’

           

What has brought this change in perception of cars amongst Australian buyers? The chief reason is probably financial. While someone outlaying $67,200 for the six-speed manual 2010 BMW 123d isn't going to be sent bankrupt by having to pay $1.30 per litre for petrol, the fact that the diesel is about 25 per cent more economical to run does come into the equation. After all, one of the best ways of making money is not spending it...

Aside from the financial situation, there's a degree of coolness in buying a turbo-diesel car that didn’t exist in Australia until recently. A coolness created by letting others know you are doing your part for the air we all breathe. And those who appreciate everything European now realise that the citizens of that continent see diesel as the way of the future.

Finally, the car makers have improved turbo-diesel engines out of sight in recent times. Like all thinking car makers, BMW has working hard at lowering emissions and fuel consumption. The German marque has been doing so for decades, thus giving it a big head start over many others when the serious talk of global warming began a few years ago.

           

Long linked with performance cars that make drivers smile, BMW made the positive decision that low emissions should not get in the way of performance and driving enjoyment.

The result is the BMW 123d convertible we have just, reluctantly, taken back to BMW’s office. The four-cylinder engine may only have a capacity of 2.0 litres, but it's highly tuned and produces 150 kW of power and 400 Newton metres of torque. Not that many years ago you would have needed a gas-guzzling 5.0-litre V8 to produce those figures. Nowadays an economical diesel will suffice.

We didn’t drive the BMW 123d for economy, instead we revelled in its acceleration and sheer grunt. Yet typically the fuel consumption was in the seven to eight litres per hundred kilometre range in around town driving. And could be brought into the sixes on the open road.

There's more to the BMW's low fuel diesel consumption than simply advanced technology, as there are times when you simply don’t use the engine. Because it has a stop-start feature that turns the engine off when the car comes to a standstill and you disengage the clutch. It restarts as soon as you push the clutch pedal down again. You do hear it starting, but it's relatively smooth and after the first few times we were barely aware it was happening.

The most important economy feature of all is an indication on the dashboard of when you should change up and down gears. Most drivers of manual cars, tend to hold onto lower gears far longer than is necessary, and thus use unnecessary fuel. BMW says this simple feature can give a bigger saving in fuel than any other of the new technologies it has added to the car.

Enough of economy and emissions, let's talk about the sheer driving pleasure of the little BMW convertible. For starters it has our preferred roof type – a soft-top. While we are well aware of the advantages of folding hardtops, there's a sense of purity of design that only a soft-top gives you.

In the 123d the roof is completely automatic. One button puts it down, another gets it back up again. It's not particularly fast and the mechanism sounds a bit clunky at times. 

             

The soft-top folds away neatly and doesn't take too much volume away from the boot. Mind you, this is a small car with rear wheel drive, so be sure to check the boot size as part of your personal road test.

Engine response is very good, but the inevitable turbo lag may irritate drives accustomed to the nearly-instantaneous actions of BMW petrol engines. Once the diesel is on song it reacts rapidly and gives the sort of throttle control keen drivers love on their favourite stretch of driving road.

Handling is simply brilliant in the usual BMW manner. The balance, steering response and feel of this convertible with the top down and the wind in the hair is sure to bring a smile to your face.

AT A GLANCE

MODEL RANGE
120i 2.0-litre petrol two-door convertible: $52,900 (manual), $55,019 (automatic)
125i 3.0-litre petrol two-door convertible: $64,700 (manual), $67,665 (automatic)
123d 3.0-litre turbo-diesel two-door convertible: $67,200 (manual), $69,480 (automatic)
135i 3.0-litre petrol two-door convertible: $80,200 (manual), $83,164 (automatic)

FEATURES
ABS Brakes: Standard in all models
Air Conditioning: Standard in all models
CD Player: Standard in all models
Central Locking: Standard in all models
Cruise Control: Standard in all models
Dual Front Airbags: Standard in all models
Front Side Airbags: Standard in all models
Stability Control: Standard in all models
Traction Control: Standard in all models

SPECIFICATIONS (BMW 123d 3.0-litre turbo-diesel two-door convertible)

ENGINE:
Engine Capacity: 1.995 litres
Configuration: Four cylinders in line
Head Design: DOHC, four valves per cylinder
Compression Ratio: 16.5:1
Bore/Stroke: 84.0 mm x 90.0 mm
Maximum Power: 150 kW @ 4400 rpm
Maximum Torque: 400 Nm @ 2000-2250 rpm

DRIVELINE:
Driven Wheels: Rear
Manual Transmission: Six-speed
Automatic Transmission: Six-speed
Final Drive Ratio: 2.81:1

DIMENSIONS, WEIGHT AND CAPACITIES:
Length: 4360 mm
Wheelbase: 2660 mm
Width: 1748 mm
Height: 1411 mm
Turning Circle: 10.7 metres
Kerb Mass: 1540 kg
Fuel Tank Capacity: 53 litres
Towing Ability: 740 kg (1200 kg with braked trailer)

SUSPENSION AND BRAKES:
Front Suspension: Double pivot spring strut
Rear Suspension: HA5 dispersed double control arm
Front Brakes: Ventilated disc
Rear Brakes: Ventilated disc

PERFORMANCE:
0-100 km/h Acceleration: 7.5 seconds

FUEL CONSUMPTION:
Type: Diesel
Combined Cycle (ADR 81/01): 5.4L/100km

GREEN VEHICLE GUIDE RATINGS:
Greenhouse Rating: 7.5/10
Air Pollution Rating: 6/10

STANDARD WARRANTY:
Three years/unlimited km