2004 SUBARU IMPREZA WRX service

4-23
Climate control
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5. Reinstall the air filter cover. 6. Connect the connector, and reinstall the glove box.
7. Close the glove box.
1) Service label
2) Caution label
8. LABEL installation 1) Fill out the information on the service label
(small).
2) Attach service and caution labels on the door pil-
lar on the driver’s side.
Contact your dealer if the following occurs,
even if it is not yet time to change the filter:
UG4052CA
UG4051BA
1
2
HS4027BB

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
! 2.5 Liter models
The 2.5 Liter engine is designed to operate using un-
leaded gasoline with an octane rating of 87 AKI or
higher. ! 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
recommended that you use premium grade unleaded
gasoline. !
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. ! 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. ! 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
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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 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 spec-
ifications. 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. ! 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 ofreformulated 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.
As additional guidance, only use fuels suited for your
vehicle as explained below. "
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 ONLYif 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

7-4
Starting and operating
these conditions. "
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. " 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
! Refueling
0
UG7501BA

7-7
Starting and operating
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State emission testing (U.S. only)
At state inspection time, remember to tell your in-
spection or service station in advance not to place
your Subaru AWD vehicle on a two-wheel dyna-
mometer. Otherwise, serious transmission dam-
age will result.
Some states have started using dynamometers in
their state inspection programs in order to meet their
obligation under federal law to implement stricter vehi-
cle emission standards to reduce air pollution from
cars. A dynamometer is a treadmill or roller-like testing
device that allows your car’s wheels to turn while the
car remains in one place. Depending on the severity of
a state’s air pollution problems, the states must adopt
either a “basic” or “enhanced” vehicle emission in-
spection test. Normally, a portion of the basic emission
test consists of an emission inspector inserting an an-
alyzer probe into the exhaust pipe of an idling vehicle
for a short period of time. States with more severe air
pollution problems are required to adopt an enhanced
vehicle emission test. This test simulates actual driv-
ing conditions on a dynamometer and permits more
accurate measurement of tailpipe emitted pollution
than the basic emission test.
The U.S. Environmental Protection Agency (EPA) and states using two-wheel dynamometers in their emis-
sion testing programs have
EXEMPTED Subaru AWD
vehicles from the portion of the testing program that in-
volves a two-wheel dynamometer.
There are some states that use four-wheel dynamom-
eters in their testing programs. When properly used,
that equipment will not damage an AWD Subaru vehi- cle.
Under no circumstances should the rear wheels be
jacked off the ground, nor should the driveshaft be dis-
connected for state emission testing.
Testing of an All-Wheel Drive vehicle must
NEVER be performed on a single two-wheel dy-
namometer. Attempting to do so will result in
uncontrolled vehicle movement and may cause
an accident or injuries to persons nearby.
Resultant vehicle damage due to improper test-
ing is not covered under the SUBARU Limited
Warranty and is the responsibility of the state

7-8
Starting and operating
inspection program or its contractors or licens-ees.
The EPA has issued regulations for inspecting the On-
Board Diagnostic (OBD) system as part of the state
emissions inspection. The OBD system is designed to
detect engine and transmission problems that might
cause vehicle emissions to exceed allowable limits.
These inspections apply to all 1996 model year and
newer passenger cars and light trucks. Several states
plus the District of Columbia have opted to start the
OBD system inspection prior to the required EPA reg-
ulation effective date of January 1, 2002. Other states
will add OBD system inspection in 2002. " The inspection of the OBD system consists of a vi-
sual operational check of the “ CHECK ENGINE” warn-
ing light/malfunction indicator lamp (MIL) and an ex-
amination of the OBD system with an electronic scan
tool while the engine is running." A vehicle passes
the OBD system inspection if
proper the “ CHECK ENGINE ” warning light/MIL illumi-
nation is observed, there is no stored diagnostic trou-
ble codes, and the OBD system readiness monitors
are complete. " A vehicle fails
the OBD inspection if the “ CHECK
ENGINE ” warning light/MIL is not properly operating or there is one or more diagnostic trouble codes stored
in vehicle’s computer with the “
CHECK ENGINE”
warning light/MIL illuminated. " A state emission inspection may reject (not pass or
fail) a vehicle if the number of OBD system readinessmonitors “ Not Ready ” is greater than three. Under this
condition, the vehicle operator should be instructed to
drive his/her vehicle for a few days to set the monitors
and return for an emission re-inspection. " Owners of rejected or failing vehicles should contact
their Subaru Dealer for service.

8-6
Driving tips
Periodic inspections
To keep your vehicle in the best condition at all times,
always have the recommended maintenance services
listed in the maintenance schedule in the “Warranty
and Maintenance Booklet” performed at the specified
time or mileage intervals.Driving in foreign countries
When planning to use your vehicle in another country: "
Confirm the availability of the correct fuel. (Refer to
the “Fuel requirements” section in chapter 7.)" Comply with all regulations and requirements of
each country.

8-37
Driving tips
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use towing mirrors that conform with Federal, state/
province and/or other applicable regulations. !Trailer lights
Connection of trailer lights to your vehicle’s electrical
system requires modifications to the vehicle’s lighting
circuit to increase its capacity and accommodate wir-
ing changes. To ensure the trailer lights are connected
properly, please consult your SUBARU dealer. Check
for proper operation of the turn signals, the brake
lights and parking lights each time you hitch up.
Direct splicing or other improper connection of
trailer lights may damage your vehicle’s electri-
cal system and cause a malfunction of your ve-
hicle’s lighting system.
! Tires
Make sure that all the tires on your vehicle are properly
inflated to the pressure specified on the tire placard lo-
cated on the left center pillar of your vehicle.
Trailer tire condition, size, load rating and proper infla-
tion pressure should be in accordance with the trailer
manufacturer’s specifications. In the event your vehicle gets a flat tire when towing a
trailer, ask a commercial road service to repair the flat
tire.
If you carry a regular size spare tire in your vehicle or
trailer as a precaution against getting a flat tire, be
sure that the spare tire is firmly secured.
Never tow a trailer when the temporary spare
tire is used. The temporary spare tire is not de-
signed to sustain the towing load. Use of the
temporary spare tire when towing can result in
failure of the spare tire and/or less stability of
the vehicle.
! Trailer towing tips
"Never exceed 45 mph (72 km/h) when towing
a trailer in hilly country on hot days. " When towing a trailer, steering, stability,
stopping distance and braking performance
will be different from normal operation. For
safety’s sake, you should employ extra caution