2006 SUBARU IMPREZA octane

7-2 Starting and operating
Starting and operatingFuel
Fuel requirements
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.
WRX
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 gas-
oline of 91 AKI or higher for WRX. If
other gasoline (lower than 91 AKI) is
used, knocking, reduced output and poor accelerator response will result.
WRX-STI
The 2.5-liter turbo engine is designed to
operate using super-premium unleaded
gasoline with an octane rating of 93 AKI or
higher. If super-premium unleaded gaso-
line with an octane rating of 93 AKI or
higher is not available, premium unleaded
gasoline with an octane rating of 91 AKI or
higher may be temporarily used. For opti-
mum engine performance and driveability,
it is required that you use super-premium
grade unleaded gasoline with an octane
rating of 93 AKI or higher.
NOTE
Be sure to use super-premium unlead-
ed gasoline of 93 AKI or higher for
WRX-STI. If other gasoline (lower than
93 AKI) is used, knocking, reduced out-
put and poor accelerator response will
result.
Fuel octane rating
This octane rating is the average of the
Research Octane and Motor Octane num-
bers and is commonly referred to as the
Anti Knock Index (AKI).
Using a gasoline with a lower octane rat-
ing 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.
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
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 Califor-
nia gasoline specifications. If you live in
any other state than California, your vehi-
cle will operate on gasoline meeting Fed-
eral specifications. Gasoline sold outside
California is permitted to have higher sul-
fur levels, which may affect the perfor-
mance of your vehicle ’s catalytic convert-
er 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
Use of a fuel which is low in quality
or use of an inappropriate fuel addi-
tive may cause engine damage.

Starting and operating 7-3
– CONTINUED –
problem is fuel related before returning
your vehicle to an authorized dealer for
service.
MMT
Some gasoline contains an octane-en-
hancing additive called MMT (Methylcy-
clopentadienyl Manganese Tricarbonyl). If
you use such fuels, your emission control
system performance may deteriorate and
the CHECK ENGINE warning light/Mal-
function indicator lamp may turn on. If this
happens, return to your authorized
SUBARU Dealer for service. If it is deter-
mined that the condition is caused by the
type of fuel used, repairs may not be cov-
ered by your warranty.
Gasoline for cleaner air
Your use of gasoline with detergent addi-
tives will help prevent deposits from form-
ing 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 continuously 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 ma-
terials called oxygenates. Use of these fu- els can also help keep the air cleaner. Ox-
ygenated blend fuels, such as MTBE (Me-
thyl Tertiary Butyl ether) or ethanol (ethyl
or grain alcohol) may be used in your ve-
hicle, but should contain no more than
15% MTBE or 10% ethanol for the proper
operation of your SUBARU.
In addition, some gasoline suppliers are
now producing reformulated gasolines,
which are designed to reduce vehicle
emissions. SUBARU approves the use of
reformulated gasoline.
If you are not sure what the fuel contains,
you should ask your service station oper-
ators if their gasolines contain detergents
and oxygenates and if they have been re-
formulated to reduce vehicle emissions.
As additional guidance, only use fuels
suited for your vehicle as explained in the
following.
Fuel should be unleaded and have an
octane rating no lower than that specified
in this manual.
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 suffi-
cient quantities of the proper cosolvents
and corrosion inhibitors required to pre- vent damage to the fuel system. Do not
use fuel containing methanol
EXCEPT un-
der these conditions.
If undesirable driveability problems are
experienced and you suspect they may be
fuel related, try a different brand of gaso-
line before seeking service at your
SUBARU dealer.
Fuel system damage or driveability
problems which result from the use of im-
proper fuel are not covered under the
SUBARU Limited Warranty.
Do not let fuel spill on the exterior
surfaces of the vehicle. Fuels con-
taining alcohol may cause paint
damage, which is not covered under
the SUBARU Limited Warranty.

GAS STATION REFERENCE
Fuel:
2.5-liter non-turbo models
Use only unleaded gasoline with an octane rating of 87 AKI or
higher.
WRX
Use premium unleaded gasoline with an octane rating of 91 AKI or
higher. If premium unleaded gasoline with an octane r ating of 91
AKI is not available, regular unleaded gasoline with octane rating
of 87 AKI or higher may be temporarily used. For opti mum engine
performance and driveability, it is required that you use premium
grade unleaded gasoline with an octane rating of 91 AKI or higher.
WRX-STI
Use super-premium unleaded gasoline with an octane rat ing of 93
AKI or higher. If super-premium unleaded gasoline wi th an octane
rating of 93 AKI is not available, premium unleaded g asoline with
octane rating of 91 AKI or higher may be temporarily u sed. For op-
timum engine performance and driveability, it is requir ed that you
use super-premium grade unleaded gasoline with an oct ane ratingof 93 AKI or higher.
Fuel octane rating
This octane rating is the average of the Research Octane
and Mo-
tor Octane numbers and is commonly referred to as the An ti 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 SM with the words “ENERGY CON-
SERVING ” and the ILSAC certification mark (starburst mark) dis-
played on the container.
Engine oil capacity:
4.2 US qt (4.0 liters, 3.5 Imp qt)
Cold tire pressure:
Item 2.5i, OUTBACK SPORT WRX WRX-STI
Tire size P205/55R16 89V 215/45R17 91W 225/45R17 90W
Wheel size 16  6 1
/2 JJ 17
 7 JJ 17  8 JJ
Pressure Front 33 psi (230 kPa, 2.3 kgf/cm 2
) 33 psi (230 kPa, 2.3 kgf/cm 2
) 36 psi (250 kPa, 2.5 kgf/cm 2
)
Rear 30 psi (210 kPa, 2.1 kgf/cm 2
) 32 psi (220 kPa, 2.2 kgf/cm 2
) 30 psi (210 kPa, 2.1 kgf/cm 2
)
Temporary spare
tire Size
T135/70 D16 T135/70 D17
Pressure 60 psi (420 kPa, 4.2 kgf/cm2
)