The 2008 GMC Sierra typically uses 5W-30 engine oil that meets API SN or higher, and Dexos1-certified oil is preferred if your specific engine specification requires it. Always confirm the exact oil type from the owner’s manual or the under-hood label for your engine variant and climate.
Recommended viscosity and grade
Oil viscosity varies by engine and climate, but most 2008 Sierra models use 5W-30 as the standard grade. The following guidelines help you pick the right oil.
- 5W-30 motor oil (synthetic or synthetic-blend) that meets API SN or a higher specification.
- Dexos1-certified 5W-30 oil if your model’s GM specification calls for Dexos1 certification.
Bottom line: 5W-30 is the baseline; Dexos1 compliance is recommended if your manual specifies it. Always verify with the manual or under-hood label.
Oil specifications to check
Because GM engines in 2008 spanned different configurations, the exact spec can vary. Use the following as a reference and verify for your engine.
- API service rating: SN or higher (and higher like SP if available) as a minimum.
- Dexos1 certification if your GM specification requires it for your engine.
- Viscosity: 5W-30 is the common standard; other grades are acceptable only if approved by GM for your engine and climate.
Using oil that meets these specs helps ensure proper lubrication, engine protection, and warranty compatibility. When in doubt, consult the owner's manual or a GM-certified technician.
Practical tips and maintenance basics
Beyond the spec sheet, consider synthetic versus conventional oil, oil change intervals based on driving conditions, and regularly checking oil level between changes.
Summary: For a 2008 GMC Sierra, the standard guidance is 5W-30 API SN (or higher) with Dexos1 certification where required by your engine variant. Always verify the exact specification in the owner’s manual or on the under-hood label to ensure you use the correct oil for your model and climate.