2007 Lexus GS 450h User Guide - Page 503

6-1. Specifications Fuel information Your vehicle must use only unleaded gasoline. Premium unleaded gasoline with an Octane Rating of 91 (Research Octane Number 96) or higher required for optimum engine performance. At minimum, the gasoline you use should meet the specifications of ASTM D4814 in the U.S.A. and CGSB3.5-M93 in Canada. n Fuel tank opening for unleaded gasoline To help prevent incorrect fueling, your Lexus has a fuel tank opening that only accommodates the special nozzle on unleaded fuel pumps. n If premium gasoline is not available If this premium fuel is not available, you may use unleaded gasoline with an Octane Rating of 87 or so (Research Octane Number 91). The use of such gasoline may cause the engine to knock or drastically reduce output to protect itself while driving with a heavy load. To avoid this, refill the tank with premium unleaded gasoline as soon as possible. n If your engine knocks l Consult your Lexus dealer. l You may occasionally notice light knocking for a short time while accelerating or driving uphill. This is normal and there is no need for concern. n Gasoline quality In very few cases, driveability problems may be caused by the brand of gasoline you are using. If driveability problems persist, try changing the brand of gasoline. If this does not correct the problem, consult your Lexus dealer. 6 Vehicle specifications 489