2003 Subaru Impreza Owner's Manual - Page 343

Maintenance and service New API Certification Mark (Starburst Mark) In choosing an oil, you want the proper quality and viscosity, as well as one that will add to fuel economy. The following table lists the recommended viscosities and applicable temperatures. When adding oil, different brands may be used together as long as they are the same API classification and SAE viscosity as those recommended by SUBARU. SAE viscosity number and applicable temperature *) 5W-30 is preferred. Engine oil viscosity (thickness) affects fuel economy. Oils of lower viscosity provide better fuel economy. However, in hot weather, oil of higher viscosity is required to properly lubricate the engine. CAUTION Use only engine oil with the recommended grade and viscosity. 11-14