How to keep my Ford Transit Custom engine running smoothly?

I recently bought a Ford Transit Custom and I noticed that the engine is not running as smoothly as it used to. I want to keep my car in top condition, but I'm not sure what maintenance tasks should I focus on. Can you give me some tips on how to ensure the engine stays running smoothly?

Regularly check and replace the engine oil to ensure proper lubrication. Also, make sure to keep an eye on the oil filter and replace it if needed.

Inspect and clean the air filter every 12,000 miles to prevent dust and debris from entering the engine.

Service your vehicle according to the manufacturer's recommended schedule, including checking and replacing spark plugs and other components as needed.