Toyota Tundra 2015, Manual, Page: 520 / 576

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9-1. Specifications
Fuel information
■
Fuel tank opening for unleaded gasoline
To help prevent incorrect fueling, your vehicle has a fuel tank opening that
only accommodates the special nozzle on unleaded fuel pumps.
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Fuel quality
In very few cases, driveability problems may be caused by the brand of fuel
you are using. If driveability problems persist, try changing the brand of fuel. If
this does not correct the problem, consult your Toyota dealer.
 Gasoline engine
You must only use unleaded gasoline in your vehicle.
Select octane rating 87 (Research Octane Number 91) or higher.
Use of unleaded gasoline 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..
 Flex-fuel engine
You must only use unleaded gasoline in your vehicle, 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..
At minimum, the E85 you use should meet the specifications of
ASTM D5798 in the U.S.A..