2007 Subaru Impreza Owner's Manual - Page 304

11-12 Maintenance and service & Recommended grade and viscosity under severe driving conditions If the vehicle is used in desert areas, in areas with very high temperatures, or is used for heavy-duty applications, use of oil with the following grade and viscosities is recommended. API classification SM (or SL): SAE viscosity No.: 30, 40, 10W-50, 20W-40, 20W-50 Cooling system WARNING Never attempt to remove the radiator cap until the engine has been shut off and has cooled down completely. Since the coolant is under pressure, you may suffer serious burns from a spray of boiling hot coolant when the cap is removed. & Synthetic oil You can 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, and must follow the oil and filter changing intervals shown in the maintenance schedule. CAUTION . The cooling system has been filled at the factory with a high quality, corrosion-inhibiting, year-around coolant which provides protection against freezing down to −338F (−368C). Subaru engines use aluminum components that require the anti-corrosive and anti-freeze properties of Subaru Genuine Coolant, which is specifically formulated for the Subaru cooling system. Failure to use Subaru Genuine Coolant along with Subaru Cooling System Conditioner at the recommended main- tenance intervals may result in problems, including, but not limited to shortened life of engine components and cooling system clogging, coolant leaks and engine damage from overheating. Problems caused by the failure to use Subaru Genuine Coolant and Subaru Cooling System Conditioner at recommended intervals are not covered under the Subaru Limited Warranty. While there may be other generic products that may provide the required protection, they have not been tested for compatibility with Subaru engines and cooling system components, and therefore they are not recommended. . Do not splash the engine coolant over painted parts. The alcohol contained in the engine coolant may damage the paint surface. & Cooling fan, hose and connections Your vehicle employs an electric cooling fan which is thermostatically controlled to operate when the engine coolant reaches a specific temperature.