Why is my Vauxhall Crossland's fuel efficiency decreasing?

I've noticed that my Vauxhall Crossland's fuel efficiency has been decreasing over the past few months. I used to get a full tank lasting me almost two weeks, but now I'm lucky if it lasts a week. What could be causing this and how can I improve my fuel efficiency?

One possible reason for your decreasing fuel efficiency could be a dirty air filter. When the air filter is clogged with dirt and debris, it can reduce the amount of air flowing into your engine, leading to a decrease in fuel efficiency. I would recommend having your air filter checked and replaced if necessary.

Another possibility could be that your tires are not properly inflated. When your tires are underinflated, it can cause your engine to work harder and use more fuel. Make sure to regularly check your tire pressure and inflate them to the recommended level.

It's also important to maintain your vehicle's regular maintenance schedule. This includes oil changes, tune-ups, and other necessary maintenance tasks. Neglecting these can lead to a decrease in fuel efficiency.