Genuine OEM Volkswagen Oil Return Line, part number 028145736. This component is marked as number 7 in the diagram and is part of the turbocharger system. Its function is to facilitate the return of oil from the turbocharger back to the engine's oil sump. Genuine OEM oil return lines are manufactured to exact specifications to prevent leaks and ensure proper lubrication, which is critical for the longevity of the turbocharger.