What are the common maintenance checks for a Ford Focus engine?

I noticed my Ford Focus's engine has been sounding a bit off lately. What are the common maintenance checks I should do to keep it in good condition?

As a previous Ford Focus owner, I recommend checking your oil and coolant levels regularly. These are important for the engine's performance and should be topped up if needed.

Another important maintenance check is to replace your air filter every 12,000 miles. This helps keep your engine clean and running efficiently.