Why has a xsara Picasso 2 lt hdi engine have 2 oil filler caps?

The Citroën Xsara Picasso 2.0L HDi engine has two oil filler caps due to its design, which includes a separate oil reservoir for the turbocharger. This configuration allows for better oil circulation and cooling, ensuring both the engine and turbo operate efficiently. It also facilitates maintenance, allowing for easier access to oil levels in both areas.