Why does the Audi A1 have a higher fuel efficiency compared to other cars?

I've noticed that the Audi A1 has a higher fuel efficiency rating than other cars in its class. Can someone explain why that is? Are there any specific features or technologies that contribute to this?

One factor that contributes to the Audi A1's high fuel efficiency is its lightweight construction. By using lightweight materials such as aluminum and carbon fiber, the car's overall weight is reduced, making it easier for the engine to power and thus improving its fuel economy.