How does the Audi A4 achieve better fuel efficiency?

I've been looking into purchasing an Audi A4 and noticed that it has good fuel efficiency ratings. Can someone explain how this car manages to achieve this and what specific features contribute to its efficiency?

The Audi A4 is equipped with a turbocharged 4-cylinder engine that uses the latest direct injection technology. This allows for a more efficient use of fuel and reduces emissions.

The A4 also utilizes a start-stop system that automatically shuts off the engine when idling and restarts it when you're ready to go. This helps save fuel and reduce emissions when stuck in traffic.