Toyota 2009 Tundra, Manual, Page: 611 / 663

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6-1. Specifications
Fuel information
n Fuel tank opening for unleaded gasoline
To help prevent incorrect fueling, your Toyota has a fuel tank opening that
only accommodates the special nozzle on unleaded fuel pumps.
Gasoline engine
Your vehicle must use only unleaded gasoline.
Select octane rating 87 (Research Octane Number 91) or higher. The
use of unleaded fuel with an octane rating lower than 87 may result
in engine knocking. Persistent knocking can lead to engine damage.
At minimum, the gasoline you use should meet the specifications
of ASTM D4814 in the U.S.A. and CGSB3.5-M93 in Canada.
Flex-fuel engine
Your vehicle must use only unleaded gasoline, E85, or a blend of the
two fuels.
Unleaded gasoline (Octane rating 87 [Research Octane Number 91]
or higher), E85, or a blend of these two fuels is required for optimum
engine performance.
The use of unleaded gasoline with an octane rating lower than 87
may result in engine knocking. Persistent knocking can lead to
engine damage.
The use of fuel with an ethanol concentration in excess of 85% will
have a negative impact on driving performance and can cause
damage to the fuel system components.
At minimum, the gasoline you use should meet the specifications
of ASTM D4814 in the U.S.A. and CGSB3.5-M93 in Canada.
At minimum, the E85 you use should meet the specifications of
ASTM D5798 in the U.S.A.