Subaru BRZ 2017 Owner's Manual page 90

1-5. Refueling
Closing the fuel tank cap
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Fuel types
Unleaded petrol, Research Octane Number of 98 or higher
If unleaded petrol with an octane rating of 98 RON is not available, unleaded
petrol with an octane rating of 95 RON may be used with no detriment to
engine durability or driveability.
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Use of ethanol blended petrol in a petrol engine
SUBARU allows the use of ethanol blended petrol where the ethanol content
is up to 10%. Make sure that the ethanol blended petrol to be used has a
Research Octane Number that follows the above.
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After refueling, turn the fuel tank
cap until you hear a click. Once
the cap is released, it will turn
slightly in the opposite direction.