Here's what I recommend:
1. Check your owner's manual: This is the most reliable source of information. It should specify the exact oil capacity for your engine.
2. Consult your local VW dealership or a qualified mechanic: They can provide you with the accurate oil capacity based on your car's specific details.
Important Note: Do not rely on general online information. The oil capacity can vary significantly between different models and engine variations.
By checking your owner's manual or consulting a professional, you'll ensure you use the correct amount of oil for your 2003 VW Passat 1.8 engine.