2008 Cadillac STS Owner's Manual - Page 338

What Kind of Engine Oil to Use Notice: If you use oils that do not have the GM4718M Standard designation, you can cause engine damage not covered by your warranty. • SAE 5W-30 As shown in the viscosity chart, SAE 5W-30 is best for your vehicle. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils such as SAE 20W-50. • Oils meeting these requirements should have the starburst symbol on the container. This symbol indicates that the oil has been certified by the American Petroleum Institute (API). Look for three things: • GM4718M Your vehicle's engine requires a special oil meeting GM Standard GM4718M. Oils meeting this standard may be identified as synthetic. However, not all synthetic oils will meet this GM standard. Look for and use only an oil that meets GM Standard GM4718M. 5-20 Look for this on the oil container, and use only those oils that are identified as meeting GM Standard GM4718M and have the starburst symbol on the front of the oil container.