2008 Subaru Impreza Owner's Manual - Page 225

Starting and operating 7-3 Fuel CAUTION Use of a fuel which is low in quality or use of an inappropriate fuel additive may cause engine damage. engine models. If other gasoline (lower than 91 AKI) is used, knocking, reduced output and poor accelerator response will result. ! WRX STI The WRX STI engine is designed to operate at maximum performance using unleaded gasoline with an octane rating of 93 AKI or higher. If 93 AKI fuel is not readily available in your area, unleaded gasoline with an octane rating of 91 AKI may be used with no detriment to engine durability or driveability. However, you may notice a slight decrease in maximum engine performance while using 91 AKI fuel. Use of 91 AKI fuel will not affect your warranty coverage. ! Fuel octane rating This octane rating is the average of the Research Octane and Motor Octane numbers and is commonly referred to as the Anti Knock Index (AKI). Using a gasoline with a lower octane rating can cause persistent and heavy knocking, which can damage the engine. Do not be concerned if your vehicle sometimes knocks lightly when you drive up a hill or when you accelerate. See your dealer or a qualified service technician if you use a fuel with the specified octane & Fuel requirements ! Non-turbo models The 2.5-liter non-turbo engine is designed to operate using unleaded gasoline with an octane rating of 87 AKI or higher. ! Turbo models ! All models except WRX STI The 2.5-liter turbo engine is designed to operate using premium unleaded gasoline with an octane rating of 91 AKI or higher. If premium unleaded gasoline is not available, regular unleaded gasoline with an octane rating of 87 AKI or higher may be temporarily used. For optimum engine performance and driveability, it is required that you use premium grade unleaded gasoline. NOTE Be sure to use premium unleaded gasoline of 91 AKI or higher for turbo rating and your vehicle knocks heavily or persistently. ! Unleaded gasoline The neck of the fuel filler pipe is designed to accept only an unleaded gasoline filler nozzle. Under no circumstances should leaded gasoline be used because it will damage the emission control system and may impair driveability and fuel economy. ! Gasoline for California-certified LEV If your vehicle was certified to California's low emission vehicle (LEV) standards as indicated on the underhood tune-up label, it is designed to optimize engine and emission performance with gasoline that meets the clean burning low-sulfur California gasoline specifications. If you live in any other state than California, your vehicle will operate on gasoline meeting Federal specifications. Gasoline sold outside California is permitted to have higher sulfur levels, which may affect the performance of your vehicle's catalytic converter and may produce a sulfur exhaust odor or smell. SUBARU recommends that you try a different brand of unleaded gasoline having lower sulfur to determine if the problem is fuel related before returning your vehicle to an authorized dealer for service. - CONTINUED -