Why is the Audi A2 considered the most efficient car in its class?

I've heard a lot about the Audi A2 being a highly efficient vehicle, with its lightweight design and innovative technology. However, I'm wondering what exactly sets it apart from other cars in its class and makes it stand out as the most efficient option?

The Audi A2 is equipped with a highly efficient petrol engine that can achieve impressive fuel economy numbers, making it a top choice for those looking for a car that won't break the bank at the pump.