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But along with the economy in the BMW come four comfortable leather seats, air-conditioning, heads-up display and a robust stereo system. Remember this car costs almost $80,000 new.
The economy has come without resorting to using the car's Eco-Pro mode which modifies the engine performance to deliver even greater economy.
This feature of the car blunts throttle response and turns down the air-conditioning and offers driving tips to reduce fuel consumption further.
BMW says Eco Pro mode can deliver a further 10 to 15 per cent fuel saving.
In this car we have extracted a cumulative 10km fuel saving by using Eco Pro mode, which is fine when roads are crowded and there is plenty of time for a leisurely drive.
However, most of the mileage so far has been in the default Comfort setting. This is the Sport edition of the 3 Series after all, so why not enjoy the model at its best?
The 1995cc common-rail direct-injection turbo-diesel engine delivers surprisingly smooth power and performance without any drama.
Like all diesel engines this one does not constantly encourage the driver to break motorway speed limits, or to squeal the tyres. Instead there is quick and efficient take-off, even with the stop-start function operating.
The only indication that you're driving a diesel is a brief judder as the motor chugs into action.
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Some critics have commented this model could do with more power, and there are a myriad of more powerful models available.
But the 320d is no slouch, and as you would expect from an eight-speed automatic gearbox it operates smoothly through the range.
The car is a real joy to drive on twisty roads, such as the Brynderwyn Hills, with hardly any body roll.
This is also where the rear-wheel drive comes into its own as the car's superbly balanced steering is responsive and smooth.
