Subaru Impreza Manuals 2012 Impreza Owner's Manual | Page 364

11-10 Maintenance and service NOTE 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. & Synthetic oil You should use synthetic engine oil that meets the same requirements given for conventional engine oil. When using synthetic oil, you must use oil of the same classification, viscosity and grade shown in this Owner’s Manual. Refer to “Engine oil” F12-4. Also, you must follow the oil and filter changing intervals shown in the Warranty and Maintenance booklet. NOTE Synthetic oil of the grade and viscosity noted in chapter 12 is the recommended engine oil for optimum engine performance. Conventional oil may be used if synthetic oil is unavailable. Cooling system WARNIN