1999 Lexus RX 300 Owners Manual - Page 420

ENGINE 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. 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. Gasolines containing MMT Some gasolines contain an octane-enhancing additive called MMT (methylcyclopentadienyl manganese tricarbonyl). Lexus does not recommend the use of gasolines that contain MMT. If fuels containing MMT are used, your emission control system may be adversely affected. The Malfunction Indicator Lamp on the instrument cluster may come on. If this happens, contact your Lexus dealer for service. 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. Improved gasolines The American Automobile Manufacturers Association (AAMA) has developed a specification of improved gasolines. The AAMA specification offers optimal fuel information for better vehicle performance and better protection of your engine. Lexus recommends the use of gasolines that meet the AAMA specification, if available, for improved drivability and emission control system. Gasolines containing alcohol Gasohol is a mixture of gasoline and ethanol. If you use gasohol in your Lexus, be sure that it is unleaded, has an octane rating no lower than 87 and does not contain more than 10% ethanol. Lexus does not recommend the use of gasolines containing methanol. If you use gasoline containing methanol, use only gasoline meeting the requirements above and also containing less than 5% methanol with cosolvents and corrosion inhibitors for methanol. 403