2003 Buick Regal Owner's Manual - Page 223
2003 Buick Regal Manual
Page 223 highlights
SAE IOW-30 is the viscosity grade recommended for your vehicle. However, you can use SAE 5W-30 if it's going to be colder than 60°F (16°C) before your next oil change. When it's very cold, colder than 0°F (-18"C), you should use an SAE 5W-30 oil. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity grade oils, such as SAE 1OW-40 or SAE 2OW-50 under any conditions. When to Change Engine Oil (GM Oil Life SystemTM) Your vehicle has a computer system that lets you know when to change the engine oil and filter. This is based on engine revolutions and engine temperature, and not on mileage. Based on driving conditions, the mileage at which an oil change will be indicated can vary considerably. For the oil life system to work properly, you must reset the system every time the oil is changed. When the system has calculated that oil life has been diminished, it will indicate that an oil change is necessary. A CHANGE OIL SOON light will come on. Change your oil as soon as possible within the next two times you stop for fuel. It is possible that, if you are driving under the best conditions, the oil life system may not indicate that an oil change is necessary for over a year. However, your engine oil and filter must be changed at least once a year and at this time the system must be reset. It is also important to check your oil regularly and keep it at the proper level. If the system is ever reset accidentally, you must change your oil at 3,000 miles (5 000 km) since your last oil change. Remember to reset the oil life system whenever the oil is changed. 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 and SAE 5W-30 synthetic oil or and SAE OW-30 oil. Both will provide easier cold starting and better protection for your engine at extremely low temperatures. 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. 5-18