What technology does the Audi A4 use to improve fuel efficiency?

I've heard that the Audi A4 is known for its great fuel efficiency. Can someone explain to me the specific technology that helps it achieve this?

The Audi A4 uses a combination of direct injection and valve lift system to increase fuel efficiency. The high-pressure fuel supply reduces fuel consumption and emissions while the valve lift system controls the opening and closing of valves for optimal fuel injection.

The Audi A4 also features a start-stop system, which automatically turns off the engine when the car is at a standstill, like in traffic or at a stop light. This helps save fuel and reduce emissions, especially in city driving.

Another contributing factor to the Audi A4's fuel efficiency is its lightweight construction. The use of lightweight materials, such as aluminum and high-strength steel, reduces the overall weight of the car, making it more fuel-efficient.