How to properly maintain the engine of a Ford S-Max?

I noticed that my Ford S-Max's engine is starting to sound rough. What should I do to prevent further damage and ensure that my car's engine performs at its best?

Regularly change the engine oil and oil filter every 5,000 to 7,500 miles to keep your engine running smoothly.

Check and replace the air filter every 15,000 miles to improve engine performance and fuel economy.