Toyota 2012 Yaris Hatchback Owner's Manual page 330

6-1. Specifications
Fuel information
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. and CGSB3.5-M93 in Canada.
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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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Gasoline quality
In very few cases, driveability problems may be caused by the brand of gas-
oline you are using. If driveability problems persist, try changing the brand of
gasoline. If this does not correct the problem, consult your Toyota dealer.
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Gasoline quality standards
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Automotive manufacturers in the U.S.A., Europe and Japan have devel-
oped a specification for fuel quality called World-Wide Fuel Charter
(WWFC), which is expected to be applied worldwide.
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The WWFC consists of four categories that are based on required emis-
sion levels. In the U.S., category 4 has been adopted.
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The WWFC improves air quality by lowering emissions in vehicle fleets,
and improves customer satisfaction through better performance.
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Recommendation of the use of gasoline containing detergent additives
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Toyota recommends the use of gasoline that contains detergent additives
to avoid the build-up of engine deposits.
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All gasoline sold in the U.S.A. contains detergent additives to clean and/
or keep clean intake systems.
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