How do I properly maintain the fuel efficiency of my Kia ProCeed?

I've noticed that the fuel efficiency of my Kia ProCeed has been decreasing over time. What steps can I take to ensure that it stays as efficient as possible?

Regularly checking and replacing your air filter can greatly improve your car's fuel efficiency.

I recommend using a fuel injector cleaner every 3,000 miles to keep your engine running smoothly.

Inflate your tires to the recommended pressure to improve your car's gas mileage.