The 2003 Ford Windstar's owner's manual is the definitive source for the recommended oil type and viscosity. While 5W-30 synthetic *might* be acceptable, it's crucial to check the manual. Using the wrong oil can damage your engine.
The manual will specify the recommended viscosity (like 5W-30, 10W-30, etc.) and whether synthetic or conventional oil is preferred or allowed. Don't rely on online advice; consult your owner's manual.
