2003 GMC Sonoma Owner's Manual - Page 281

As in the chart shown previously, SAE 5W-30 is the only viscosity grade recommended for your vehicle. You should look for and use only oils which have the API Starburst symbol and which are also identified as SAE 5W-30. If you cannot find such SAE 5W-30 oils, you can use an SAE IOW-30 oil which has the API Starburst symbol, if it's going to be 0°F (-18°C) or above. Do not use other viscosity grade oils, such as SAE IOW-40 or SAE 20W-50 under any conditions. Engine Oil Additives Don't add anything to your oil. The recommended oils with the starburst symbol are all you will need for good performance and engine protection. When to Change Engine Oil If any one of these is true for you, use the short tripkity maintenance schedule: Most trips are less than 5 miles (8 km). This is particularly important when outside temperatures are below freezing. Most trips include extensive idling (such as frequent driving in stop-and-go traffic). You frequently tow a trailer or use a carrier on top of your vehicle. The vehicle is used for delivery service, police, taxi or other commercial application. Driving under these conditions causes engine oil to break down sooner. If any one of these is true for your vehicle, then you need to change your oil and filter every 3,000 miles (5 000 km) or 3 months - whichever occurs first. Notice: Use only engine oil with the American Petroleum Institute Certified For Gasoline Engines starburst symbol. Failure to use the recommended oil can result in engine damage not covered by your warranty. GM Goodwrench@oil meets all the requirements for your vehicle. If you are in an area of extreme cold, where the temperature falls below -20°F (-29"C), it is recommended that you use either an SAE 5W-30 synthetic oil or an SAE OW-30 oil. Both will provide easier cold starting and better protection for your engine at extremely low temperatures. 5-18