What are the most important maintenance tasks for the Ford Focus engine?

I've recently bought a used Ford Focus and I want to make sure it stays in good condition. What are the essential maintenance tasks I should keep in mind for the engine?

Regularly changing the oil and oil filter is crucial for maintaining the health of your engine. Make sure to follow the recommended intervals in your owner's manual and use high-quality oil and filters.

Keep an eye on your coolant levels and always make sure it's topped up to the recommended level. This will help prevent your engine from overheating and causing damage.

Regularly inspect and replace your spark plugs as needed. These help ignite the fuel in your engine and worn out spark plugs can decrease performance and fuel efficiency.