What is the best method for improving the performance of a Ford Fiesta's engine?

I've been noticing a decrease in my Ford Fiesta's fuel efficiency and overall performance. What can I do to improve its engine performance and get the most out of my car?

Regularly changing your engine oil and filter can greatly improve your Ford Fiesta's performance by ensuring all the parts are properly lubricated and reducing engine wear.

Another important factor to consider for better engine performance is the type of fuel you use. Higher octane fuel can improve engine efficiency and power.