How do I improve fuel efficiency in my Volkswagen Golf?

I've noticed that my Volkswagen Golf is not as fuel efficient as it used to be. What steps can I take to improve its fuel efficiency?

Regularly check and replace your air filter.

Avoid driving at high speeds and try to maintain a steady speed on the highway.

Consider using a fuel additive that can clean your engine and improve fuel efficiency.

Ensure your tires are properly inflated and aligned.

Use cruise control whenever possible to maintain a constant speed.