1997 Chevrolet Corvette Owner's Manual - Page 249

RECOMMENDED SAE VISCOSITY GRADE ENGINE OILS FOR BEST FUEL ECONOMY AND COLD STARTING, SELECT THE LOWEST SAE VISCOSITY GRADE OIL FOR THE EXPECTED TEMPERATURE RANGE. SAE 5W-30 As shown in the viscosity chart, SAE 5W-30 is best for your vehicle. However, you can use SAE 1OW-30 if it's going to be 0°F (-18°C) or above. 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 also have the "Starburst" symbol on the container. I HOT WEATHER LOOK FOR MIS SYMBOL COLD WEATHER DO NOT USE SAE 2OW-50 OR ANY OTHER GRADE OIL NOT RECOMMENDED This symbol indicates that the oil has been certified by the American Petroleum Institute (API). Do not use any oil which does not carry this Starburst symbol. You should look for this on the oil container, and use only those oils that are identified as meeting GM Standard 47 18M and have the Starburst symbol on the front of the oil container.