1996 Lexus GS 300 Owners Manual - Page 182

ENGINE FUEL Fuel type Your vehicle must use only unleaded gasoline. To help prevent gas station mix-ups, your Lexus has a smaller fuel tank opening. The special nozzle on pumps with unleaded fuel will fit it, but the larger nozzle on pumps with leaded gas will not. If your engine knocks...If you detect heavy knocking even when using the recommended fuel, or if you hear steady knocking while holding a steady speed on level roads, consult your Lexus dealer. However, now and then, you may notice light knocking for a short time while accelerating or driving up hills. This is no cause for concern. NOTICE Do not use leaded gasoline. Use of leaded gasoline will cause the three-way catalytic converter to lose its effectiveness and the emission control system to function improperly. Also, this can increase maintenance costs. Gasolines containing detergent additives Lexus recommends use of gasolines that contain detergent additives to avoid build-up of engine deposits. For further details, ask your Lexus dealer or a local gasoline retailer. Gasolines containing MTBE Gasolines that contain MTBE (Methyl Tertiary-Butyl Ether) are available in the market. If you use a gasoline mixed with MTBE, make certain that it does not contain more than 15% of MTBE. If the use of gasolines containing MTBE causes poor driveability and/or poor fuel economy, you should stop using them. Octane number Select premium unleaded gasoline with a Research Octane Number of 96 (Octane Rating 91) or higher for optimum engine performance. However, if such premium type cannot be obtained, you may temporarily use unleaded gasoline with an octane number as low as 91. Use of unleaded fuel with an octane number or rating lower than stated above will cause persistent heavy knocking. If severe, this will lead to engine damage. 168