Lexus GS430 - Fuel Information

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6-1. Specifications
Fuel information
■ Fuel tank opening for unleaded gasoline
To help prevent incorrect fueling, your Lexus has a fuel tank opening that only
ac
commodates the special nozzle on unleaded fuel pumps.
■ If premium gasoline is not available
If 91 Octane cannot be obtained, you may use unleaded gasolin
e with an Octane
Rating as low as 87 (Research Octane Number 91). 
However, use of unleaded fuel with an Octane Rating lower than 91 may result in
engine knocking (G
S350 only: or drastically reduce output to protect itself while
driving with heavy load). Persistent knocking can lead to engine damage and
should be corrected by refueling with higher octane unleaded gasoline.
■ If your engine knocks
● Consult your Lexus dealer.
● 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.
■ 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.
Your vehicle must use only unleaded gasoline.
Premium unleaded gasoline with an Octane Rating 91 (Research Octane
Number 9
6) 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.