2005 Subaru Legacy Owner's Manual - Page 357

Starting and operating Fuel Starting and operating NOTE Use of a fuel which is low in quality or use of an inappropriate fuel additive may cause engine damage. Be sure to use premium unleaded gasoline of 91 AKI or higher for a 2.5-liter turbo engine model. If other gasoline (lower than 91 AKI) is used, knocking, reduced output and poor accelerator response will result. ! 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. ! 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. ! California fuel If your vehicle was certified to California Emission ! Fuel requirements ! 2.5-liter 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. ! 2.5-liter turbo models and 3.0-liter models The 2.5-liter turbo engine and 3.0-liter engine are 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 (for 2.5-liter turbo models), and recommended (for 3.0-liter models) that you use premium grade unleaded gasoline. 7-2