ENGINE OILLook for three things:
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).Notice: Use only engine oil identified as meeting GM Standard GM6094M and showing the American Petroleum Institute Certified For Gasoline Engines starburst symbol. Failure to use the recommended oil can result in engine damage not covered by the vehicle warranty. COLD TEMPERATURE OPERATIONIf in an area of extreme cold, where the temperature falls below -20°F (-29°C), use either an SAE 5W-30 synthetic oil or an SAE 0W-30 engine oil. Both provide easier cold starting for the engine at extremely low temperatures. Always use an oil that meets the required specification, GM6094M.ENGINE OIL ADDITIVES / ENGINE OIL FLUSHESDo not add anything to the oil. The recommended oils with the starburst symbol that meet GM Standard GM6094M are all that is needed for good performance and engine protection.Engine oil system flushes are not recommended and could cause engine damage not covered by the vehicle warranty.
Synthetic oil does ot provide better gas mileage, just better protection for a longer period of time, as the viscosity breaks down slower.