* 5W-20: This is a common viscosity for newer vehicles and is a good starting point if you don't have the owner's manual.
* Or possibly 5W-30: Older engines or those in hotter climates might call for a slightly thicker oil like 5W-30.
Crucially: Always check your owner's manual. It will specify the exact type and viscosity of oil recommended by Ford for your specific 2005 Taurus engine. This information is critical for maintaining your engine's health and warranty (if applicable).