2005 SUBARU IMPREZA octane

7-2
Starting and operating
Starting and operatingFuel
Use of a fuel which is low in quality or use of an
inappropriate fuel additive may cause engine
damage.
„ Fuel requirements
T 2.5-liter 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. T 2.0-liter turbo models
The 2.0-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
available, 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 gaso-
line. T
2.5-liter turbo model
The 2.5-liter turbo engine is designed to operate using
super-premium unleaded gasoline with an octane rat-
ing of 93 AKI or higher. If super-premium unleaded
gasoline with an octane rating of 93 AKI or higher is
not available, premium unleaded gasoline with an oc-
tane rating of 91 AKI or higher can be used. For opti-
mum engine performance and driveability, it is recom-
mended that you use super-premium grade unleaded
gasoline with an octane rating of 93 AKI or higher. T Fuel octane rating
This octane rating is the average of the Research Oc-
tane and Motor Octane numbers and is commonly re-
ferred 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 some-
times 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
rating and your vehicle knocks heavily or persistently. T Unleaded gasoline
The neck of the fuel filler pipe is designed to accept
only an unleaded gasoline filler nozzle. Under no cir-
cumstances should leaded gasoline be used because
it will damage the emission control system and may

7-3
Starting and operating
– CONTINUED –
impair driveability and fuel economy. TGasoline for California-certified LEV
Your vehicle was certified to California’s low emission
vehicle (LEV) standards as indicated on the under-
hood tune-up label. It is designed to optimize engine
and emission performance with gasoline that meets
the clean burning low-sulfur California gasoline speci-
fications. If you live in any other state than California,
your vehicle will operate on gasoline meeting Federal
specifications. Gasoline sold outside California is per-
mitted 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 having lower sulfur to determine if
the problem is fuel related before returning your vehi-
cle to an authorized dealer for service. T MMT
Some gasoline contains an octane-enhancing additive
called MMT (Methylcyclopentadienyl Manganese Tri-
carbonyl). If you use such fuels, your emission control
system performance may deteriorate and the CHECK
ENGINE warning light/Malfunction indicator lamp may
turn on. If this happens, return to your authorized
SUBARU Dealer for service. If it is determined that the
condition is caused by the type of fuel used, repairs may not be covered by your warranty. T
Gasoline for cleaner air
Your use of gasoline with detergent additives will help
prevent deposits from forming in your engine and fuel
system. This helps keep your engine in tune and your
emission control system working properly, and is a
way of doing your part for cleaner air. If you continu-
ously use a high quality fuel with the proper detergent
and other additives, you should never need to add any
fuel system cleaning agents to your fuel tank.
Many gasolines are now blended with materials called
oxygenates. Use of these fuels can also help keep the
air cleaner. Oxygenated blend fuels, such as MTBE
(Methyl Tertiary Butyl ether) or ethanol (ethyl or grain
alcohol) may be used in your vehicle, but should con-
tain no more than 15% MTBE or 10% ethanol for the
proper operation of your SUBARU.
In addition, some gasoline suppliers are now produc-
ing reformulated gasolines, which are designed to re-
duce vehicle emissions. SUBARU approves the use of reformulated gasoline.
If you are not sure what the fuel contains, you should
ask your service station operators if their gasolines
contain detergents and oxygenates and if they have
been reformulated to reduce vehicle emissions.

7-4
Starting and operating
As additional guidance, only use fuels suited for your
vehicle as explained below.y
Fuel should be unleaded and have an octane rating
no lower than that specified in this manual.y Methanol (methyl or wood alcohol) is sometimes
mixed with unleaded gasoline. Methanol can be used
in your vehicle ONLY if it does not exceed 5% of the
fuel mixture AND if it is accompanied by sufficient
quantities of the proper cosolvents and corrosion in-
hibitors required to prevent damage to the fuel system.
Do not use fuel containing methanol EXCEPT under
these conditions. y If undesirable driveability problems are experienced
and you suspect they may be fuel related, try a differ-
ent brand of gasoline before seeking service at your
SUBARU dealer. y Fuel system damage or driveability problems which
result from the use of improper fuel are not covered
under the SUBARU Limited Warranty.
Do not let fuel spill on the exterior surfaces of
the vehicle. Fuels containing alcohol may
cause paint damage, which is not covered un-
der the SUBARU Limited Warranty. „
Fuel filler lid and cap
T Refueling
0
UG7501BA

GAS STATION REFERENCE
Fuel: T2.5-liter non-turbo models
Use only unleaded gasoline with an octane rating of 87 AKI
or higher. T 2.0-liter turbo models
Use premium unleaded gasoline with an octane rating of 91
AKI or higher. If premium unleaded gasoline is not avail-
able, regular unleaded gasoline with octane rating of 87
AKI or higher may be temporarily used. For optimum en-
gine performance and driveability, it is required that you
use premium grade unleaded gasoline. T 2.5-liter turbo models
Use premium unleaded gasoline with an octane rating of 93
AKI or higher. If premium unleaded gasoline with an octane
rating of 93 AKI is not available, premium unleaded gaso-
line with octane rating of 91 AKI or higher may be tempo-
rarily used. For optimum engine performance and driveabil- ity, it is required that you use premium grade unleaded gas-
oline with an octane rating of 93 AKI or higher. „
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). Refer to “ Fuel” section in this
manual. Fuel capacity:
15.9 US gal (60 liters, 13.2 Imp gal) Engine oil:
Use only API classification SL with the words “ENERGY
CONSERVING” and the New API certification mark (star-
burst mark) displayed on the container. Engine oil capacity:
4.2 US qt (4.0 liters, 3.5 Imp qt)
Cold tire pressure:
*1: The recommended cold tire pressure for the 215/45R17 87W tire is not indicated on the vehicle placard attached to the
driver’s side B-pillar since this tire is a dealer option for the WRX. If your vehicle is equipped with 215/45R17 87W tires, be
sure to adjust them to the air pressure shown on this page.
ItemRS, RS sport package, WRXWRX (option tire) *1WRX-STi
Tire sizeP205/55R16 89V215/45R17 87W225/45R17 90W
Wheel size16
× 6 1
/2 JJ17
× 7 JJ17 × 8 JJ
PressureFront32 psi (220 kPa, 2.2 kgf/cm 2
)33 psi (230 kPa, 2.3 kgf/cm 2
)36 psi (250 kPa, 2.5 kgf/cm 2
)
Rear29 psi (200 kPa, 2.0 kgf/cm 2
)32 psi (220 kPa, 2.2 kgf/cm 2
)30 psi (210 kPa, 2.1 kgf/cm 2
)
Temporary
spare tireSizeT135/70 D16T135/70 D17
Pressure60 psi (420 kPa, 4.2 kgf/cm 2
)