IF YOU thought you had to buy a hybrid to save the planet and ease your conscience, think again. A range of new super-lean diesel small cars from European brands, and South Korea's Hyundai, are showing that the petrol-electric Toyota Prius and Honda Civic are not the only cars you can buy to reduce your impact on the environment. Using an average of just 4.5L/100km of diesel, the A3 TDIe is officially just 0.1L/100km thirstier than the Prius. If you do a lot of country driving, the diesel will use considerably less than the Toyota. Rather than create an all new drivetrain for its "e" model, Audi instead made a series of small changes that add up. Gear ratios are longer in third and fifth, the ECU has been tweaked, the suspension has been lowered, low-resistance tyres have been fitted and the hub-cabs have been designed with aerodynamics in mind. The engine is a 1.9 turbo-diesel used in the VW Golf and Skoda Octavia.