Why is my Audi A4's gas mileage decreasing?

I've noticed that the gas mileage on my Audi A4 has been decreasing over the past few months. What could be causing this issue and how can I fix it?

One potential reason for decreasing gas mileage could be a dirty air filter. Make sure to regularly clean or replace your air filter to improve fuel efficiency.

Another factor to consider is your driving habits. Aggressive driving, such as quick acceleration and braking, can significantly decrease gas mileage. Try to drive more smoothly and efficiently to improve fuel efficiency.