1999 Lexus RX 300 Owners Manual - Page 419

ENGINE FUEL Fuel type Your vehicle must use only unleaded gasoline. To help prevent gas station mixups, 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. At a minimum, the gasoline you use should meet the specifications of ASTM D4814 in the U.S.A. and CGSB 3.5-M93 in Canada. Octane rating Select Octane Rating 87 (Research Octane Number 91) or higher. For improved vehicle performance, the use of premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher is recommended. Use of unleaded fuel with an Octane Rating or Research Octane Number lower than stated above will cause persistent heavy knocking. If it is severe, this will lead to engine damage. NOTICE Do not use leaded gasoline. Use of leaded gasoline will cause the three-way catalytic converter/warm up three-way catalytic converter to lose its effectiveness and the emission control system to function improperly. Also, this can increase maintenance costs. 402