The 2005 Buick Century generally uses 5W-30 engine oil, with about 4.5 quarts required for a full oil change. Both conventional and synthetic 5W-30 oils are acceptable, and you should verify the exact specification in your owner's manual or on the oil cap for your particular vehicle.
Oil specifications for the 2005 Buick Century
The Century from this era commonly uses a 3.1-liter V6 engine, which calls for 5W-30 oil. This viscosity works across a broad range of climates, and the oil may be conventional or synthetic. Dexos certification was not mandatory for a 2005 model year, so oils that meet standard API gasoline engine specifications are appropriate as long as they are 5W-30 and suitable for your driving conditions.
To help you quickly verify the appropriate oil options, the following list outlines the standard choices for this model year.
- Viscosity: 5W-30 (the recommended standard for the 2005 Century)
- Oil type: Conventional (mineral) oil or full synthetic 5W-30 can be used
- Oil capacity: Approximately 4.5 quarts with a new filter
- Quality/spec: Oils should meet API gasoline engine service specifications (e.g., API SN or newer where applicable)
In practice, using a quality 5W-30 oil—whether conventional or synthetic—is the typical approach for reliable performance. Always confirm exact requirements with the owner's manual and follow the recommended change intervals for your driving conditions.
Summary
For a 2005 Buick Century, the standard oil type is 5W-30, usable in either conventional or synthetic form, with an oil capacity of about 4.5 quarts including the filter. Verify the precise specification in your manual or on the oil cap, and choose a well-rated oil that meets API gasoline engine standards for best results.