Fuel; Fuel Requirements - Subaru 2008 Impreza Owner's Manual

Fuel

CAUTION
Use of a fuel which is low in quality
or use of an inappropriate fuel
additive may cause engine damage.
& Fuel requirements
! Non-turbo models
The 2.5-liter non-turbo engine is designed
to operate using unleaded gasoline with
an octane rating of 87 AKI or higher.
! Turbo models
! All models except WRX STI
The 2.5-liter turbo engine is designed to
operate using premium unleaded gasoline
with an octane rating of 91 AKI or higher. If
premium unleaded gasoline is not avail-
able, regular unleaded gasoline with an
octane rating of 87 AKI or higher may be
temporarily used. For optimum engine
performance and driveability, it is required
that you use premium grade unleaded
gasoline.
NOTE
Be sure to use premium unleaded
gasoline of 91 AKI or higher for turbo
engine models. If other gasoline (lower
than 91 AKI) is used, knocking, re-
duced output and poor accelerator
response will result.
! WRX STI
The WRX STI engine is designed to
operate at maximum performance using
unleaded gasoline with an octane rating of
93 AKI or higher. If 93 AKI fuel is not
readily available in your area, unleaded
gasoline with an octane rating of 91 AKI
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
fuel. Use of 91 AKI fuel will not affect your
warranty coverage.
! 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.
Do not be concerned if your vehicle
sometimes knocks lightly when you drive
up a hill or when you accelerate. See your
dealer or a qualified service technician if
you use a fuel with the specified octane
Starting and operating
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 Cali-
fornia gasoline specifications. If you live in
any other state than California, your
vehicle will operate on gasoline meeting
Federal specifications. Gasoline sold out-
side California is permitted to have higher
sulfur levels, which may affect the perfor-
mance 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
having lower sulfur to determine if the
problem is fuel related before returning
your vehicle to an authorized dealer for
service.
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