What is the cause of poor fuel economy in Audi 80 cars?

I have been noticing a significant decrease in fuel economy in my Audi 80 lately. I am wondering what could be causing this issue.

One potential cause of poor fuel economy in Audi 80 cars could be a clogged or dirty air filter. This restricts airflow to the engine, decreasing its efficiency and resulting in higher fuel consumption.

Another common issue that can lead to poor fuel economy in Audi 80 cars is a faulty oxygen sensor. This can cause the engine to run too rich, using more fuel than necessary.