Small cars are not always as green as you think. Take, for instance, a 1.4 litre Vauxhall Corsa: it'll do no more to the gallon than the bigger Vauxhall Astra 1.4, even though the Astra will carry more passengers in greater comfort. And if you buy a 1.6 litre Astra, it'll not only be quicker, it'll drink a bit less fuel.
But with the A2, Audi have come up with a totally new approach, spending five years looking at what makes a small car worth getting into. Choosing an engine that sips like a shy teetotaller will get you only so far down the road to economy. A more fundamental remedy is to shed the workload. Steel might be strong and abundant, but the price of its strength is its weight.
The alternative lies in a chance discovery by a Provence peasant. Toiling away with a spade in a field at Les Baux, he noticed that the rock contained something that looked handy for wrapping around an oven-ready chicken. Okay, that's a gross approximation, but Bauxite rock is where the aluminium story starts. Aluminium soon became steel's foil - and car makers have grown increasingly interested in it. It's 43% lighter than steel and can be stretched so that you only need make it thick where the thickness is really necessary.
Having played around with the substance for the frame of the AL2 concept, it was just a short move for Audi to produce what you see here: a car that weighs just 895kg. With a handicap like that, either choice of engine (petrol or diesel turbo, both 1.4) has a flying start. The petrol car's average is 46.3mpg, while the diesel offers an aggregate 67.3. And an aluminium car will never rust.
The A2 is a head-on challenge to the Merc A-class. When it gets here in September (the diesel will come next January) it will cost from around £13,500 - a premium price for anyone who's not afraid of displaying willingness to invest in advanced technology.
Keen to show off the idea, Audi plans to build 60,000-70,000 A2s in year one and says the project is profit-making, even though many maintain that such claims are PR bravado. Whatever the truth, there's no doubt that you'll be paying an R&D premium.
However, this is no rip off. The A2 is a fine showcase for zero-year styling - something like an Audi TT that is halfway through a mangle. Check the wiperless rear window, the gawky angular door glass and peak-a-boo glimpses of brushed aluminium buried in the trim. For anyone still scarred by the Metro, it's proof that small is sexy.
Some limits, however, call into question its ability to blood the Merc A-class's nose. The third seat in the back will be an optional extra while, up front, the gearstick is a little close to the passenger seat and could lead to accidental groping. Storage is adequate and the dash is skinned in a pleasant, grippy surface that prevents phone slippage on most corners. In the back, deep footwells are made possible by delving into the sandwich floor construction, thus allowing lanky adults to ride unconfined. It's roomy, but no A-class killer.
The posh looks are complemented by a polished drive. It's smooth, refined and (apart from wind noise around the single front wiper), hushed. The petrol version falls flat a little in third and is no lunger, but the diesel is a tremendously thrilling alternative. It has so much torque in any gear, at any time, that you'd be barmy to buy September's petrol option, and should wait for the new year for the TDI. The diesel does make a bit of a racket because Audi's quest for low weight led them to omit the same degree of soundproofing (so saving a fiver on build costs). But after the chorus of groans from media guinea pigs, they say they will be coughing up the cash and muffling the thing. When that's done the diesel option's charm, practicality and class-leading fuel economy will make it a small wonder.
Audi A2 1.4 petrol/TDI
For: futuristic, stylish, swanky
Against: Only four seats
Top speed: 107mph
Acceleration: 0-62mph in 12 secs (diesel 12.3)
Engine: 1.4 petrol or turbodiesel, both 75bhp
On the stereo: No heavy metal
In the holdall: Organic sandwiches, wrapped in foil
