Why do some Audi A3 models have better fuel efficiency?

I recently noticed that some Audi A3 models tend to have better fuel efficiency than others. Is this due to a specific feature or technology?

The Audi A3 e-tron model uses a hybrid drivetrain, which combines a traditional gas engine with an electric motor. This allows for better fuel efficiency and reduced emissions.

The base model of the Audi A3 has a smaller engine compared to higher trim levels. This means it has less power, but it also results in better fuel economy.