Subaru WRX & WRX STI Manuals 2015 WRX & WRX STI Owner's Manual | Page 330

Starting and operating/Fuel

Fuel
CAUTION
Use of a fuel which is low in quality
or use of an inappropriate fuel
additive may cause engine damage.

& Fuel requirements
! STI
The engine is designed to operate at
maximum performance using unleaded
gasoline with an octane rating of 93 AKI
(98 RON) or higher. If 93 AKI (98 RON)
fuel is not readily available in your area,
unleaded gasoline with an octane rating of
91 AKI (95 RON) may be used with no
detriment to engine durability or driveability. However, you may notice a slight
decrease in maximum engine performance while using 91 AKI (95 RON) fuel.
Use of 91 AKI (95 RON) fuel will not affect
your warranty coverage.
! Except STI
The engine is designed to operate using
unleaded gasoline with an octane rating
of 91 AKI (95 RON) or higher. If 91 AKI
(95 RON) fuel is not readily available,
unleaded gasoline with an octane rating of

87 AKI (90 RON) may be temporarily
used.
For optimum engine performance and
driveability, it is recommended that you
use premium grade unleaded gasoline.
Regular unleaded gasoline with an octane
rating of 87 AKI (90 RON) or higher may
also be used. Using regular unleaded
gasoline will not be detrimental to engine
durability, nor will it affect your warranty
coverage. However, depending on your
driving habits and conditions, you may
notice a decrease in maximum engine
performance, fuel economy or slight engine vibration or knocking. If you experience any of these conditions while using a
lower octane rated fuel, you may want to
return to using 91 AKI (95 RON) octane
rated fuel as soon as possible. Additionally, if your vehicle knocks heavily or
persistently, the use of 91 AKI (95 RON)
or higher grade unleaded gasoline is
required.
! Fuel octane rating
This octane rating is the average of the
Research Octane and Motor Octane
numbers and is commonly referred to as
the Anti Knock Index (AKI).
Using a gasoline with a lower octane
rating can cause persistent and heavy
knocking, which can damage the engine.

7-3

Do not be concerned if your vehicle
sometimes knocks lightly when you drive
up a hill or when you accelerate. Contact
your SUBARU dealer if you use a fuel with
the specified octane rating and your
vehicle knocks heavily or persistently.
! Unleaded gasoline
The neck of the fuel filler pipe is designed
to accept only an unleaded gasoline filler
nozzle. Under no circumstances should
leaded gasoline be used because it will
damage the emission control system and
may impair driveability and fuel economy.
! Gasoline for California-certified
LEV
If your vehicle was certified to California’s
low emission vehicle (LEV) standards as
indicated on the underhood tune-up label,
it is designed to optimize engine and
emission performance with gasoline that
meets the clean burning low-sulfur California gasoline specifications. If you live in
any other state than California, your
vehicle will operate on gasoline meeting
Federal specifications. Gasoline sold outside California is permitted to have higher
sulfur levels, which may affect the performance of your vehicle’s catalytic converter
and may produce a sulfur exhaust odor or
smell. SUBARU recommends that you try
a different brand of unleaded gasoline
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