* Viscosity: Consult your owner's manual. It will specify the recommended viscosity grades, typically something like 5W-30 or 10W-30. Using the incorrect viscosity can lead to poor performance and engine damage. The manual is the ultimate authority.
* Type: Your 2000 DeVille likely recommends a conventional oil. However, you *can* use synthetic blend or full synthetic oil. Synthetic oils offer better protection and longevity, but cost more. If you're using a conventional oil, stick to a high-quality brand. Again, check your manual for any specific recommendations regarding oil type.
* API Certification: Look for an oil that meets or exceeds the API (American Petroleum Institute) service classification recommended in your owner's manual. This is usually a designation like "SM" or "SN" (older standards like SJ might be listed, but newer is better).
In short: Check your owner's manual! It's the most important source of information. Look for the recommended viscosity grade and API certification. Then choose a high-quality conventional, synthetic blend, or full synthetic oil that meets those specifications. If you can't find your manual, a reliable parts store employee can help you find the right oil based on your vehicle's year, make, and model.
