Why does the Audi A5 have a fuel efficiency of 31 mpg?

I've been researching different cars and I noticed that the Audi A5 has a fuel efficiency of 31 mpg. Can anyone explain why this is? Is it because of the engine or some other factor?

The Audi A5's 31 mpg fuel efficiency is due to its lightweight design and fuel-efficient engine. The use of lightweight materials helps make the car more aerodynamic, making it easier to move through the air with less effort. Couple that with a fuel-efficient engine and you have a car that can go farther with less gas.