It's clean, it's mean, it's Citroen's C3 Airdream.

Citroen's new DS3 line-up has been stealing the limelight recently with its style, flair and impressive driving experience marking the arrival of a long-threatened return to form by the French manufacturer.

Meanwhile, the model on which the DS3 is based sits in its flamboyant sibling's shadow. Unveiled shortly before the DS3, the latest generation C3 doesn't deserve to be overlooked. In fact, its stylish form, spacious interior and competent groundwork are what made the DS3 a possibility and have played an important role in its success.

The C3 is also cheaper, and proves even more cost-effective in Airdream+ specification.

The current UK car taxation system is awash with numbers – CO2 ratings, benefit-in-kind percentage rates and showroom tax figures, but the key number of 100 is an easy one to get your head round. It's the cut-off point for paying road tax in CO2 grams per kilometre, and it's a figure that the Airdream+ slots under with 99g/km emissions.

The road-tax free status comes courtesy of a 90bhp 1.6-litre turbo diesel engine, which also offers 74.3mpg on the combined cycle.

The C3 Airdream+ is one of the least obvious hyper-milers in terms of the driver input required. The only real clue to the excellent efficiency from the driver's seat comes in the form of the gear ratios.

The five-speed manual gearbox uses a longer final drive ratio to bring revs, fuel consumption and emissions down. All the gears feel longer, but it fails to detract from the driving experience. If anything, it makes progress more relaxed.

That fuel-saving transmission would not be possible without sufficient engine torque, but the 1.6-litre HDi proves extremely capable. Torque is available from sufficiently low down in the rev-range to make town driving undemanding and there's little in the way of turbo lag.

For more performance, there's a respectable amount of power to be found without having to work the engine too hard, meaning the C3 Airdream+ has little trouble keeping up with traffic, despite the high efficiency. A diesel particulate filter also improves its eco-credentials.

The name Airdream+ hints at something a little extra, but not just mpg. Based on the mid-specification VTR+ model, the Airdream+ far from skimps on the equipment, despite lightness often playing a key role in car manufacturer's low emissions models. Air-conditioning, full electric windows, 15in alloy wheels, cruise control and chrome trim inside mirror the VTR+. Bluetooth and parking sensors are beyond the call of duty.

The C3 Airdream+ also benefits from Citroen's Zenith panoramic, which allows the roof lining to be pushed back exposing more windscreen.

The dome-shaped body lends itself to a roomy interior feel and despite the compact size – it's one of the smallest in the B-segment – Citroen claims the C3 boasts the most capacious boot at 300 litres.

The DS3 may be getting the headlines, but with five doors, chic styling, lower purchase prices and impressive economy, the C3 Airdream+ is the small Citroen for drivers who like to be seen to be sensible, rather than simply seen.

price: Citroen C3 Airdream+ 1.6 HDi 90, �14,590 on the road

Engine: 1.6-litre diesel unit developing 90bhp and 170lb/ft of torque

Transmission: Five-speed manual transmission, driving the front wheels

Performance: 0-62mph 11.5 seconds; top speed 112mph

CO2 emissions: 99g/km

Economy: 74.3mpg