2008 Toyota Prius Owners Manual - Page 395

4-3. Do-it-yourself maintenance n Recommended viscosity SAE 5W-30 is the best choice for good fuel economy, and good starting in cold weather. *: If Outside temperature SAE 5W-30 oil is not available, SAE 10W-30 oil may be used. However, it should be replaced with SAE 5W-30 at the next oil change. n How to read oil container labels The ILSAC (International Lubricant Standardization and Approval Committee) Certification Mark is added to some oil containers to help you select the oil you should use. 368 PRIUS_U_(L/O_0802)