Lexus RX300 Manual page 259

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.
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.
maintenance costs.
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.
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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 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)
Also, this can increase 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.