2003 Subaru Impreza Owner's Manual - Page 231

Starting and operating Fuel CAUTION Use of a fuel which is low in quality or use of an inappropriate fuel additive may cause engine damage. J Fuel requirements B 2.5 Liter models The 2.5 Liter engine is designed to operate using unleaded gasoline with an octane rating of 87 AKI or higher. B 2.0 Liter (turbo) models The 2.0 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 recommended that you use premium grade unleaded gasoline. B 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 rating and your vehicle knocks heavily or persistently. B 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. B Gasoline for California-certified LEV 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 7-2