Subaru 2009 Impreza Owner's Manual page 407

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Fuel:
! Non-turbo models
Use only unleaded gasoline with an octane rating of 87 AKI or
higher.
! Turbo models except WRX STI
Use premium unleaded gasoline with an octane rating of 91 AKI
or higher. If premium unleaded gasoline with an octane rating of
91 AKI is not available, regular unleaded gasoline with 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 with an octane
rating of 91 AKI or higher.
! WRX STI
The 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
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Cold tire pressure:
Tire size
Wheel size
Pressure
Front
Rear
Temporary spare tire Size
Pressure
GAS STATION REFERENCE
P205/55R16 89V P205/50R17 88V
1
16 6 / JJ
2
T125/70 D17
performance while using 91 AKI fuel. Use of 91 AKI fuel will
not affect your warranty coverage.
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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 the "Fuel" section in this manual.
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Fuel capacity:
16.9 US gal (64 liters, 14.1 Imp gal)
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Engine oil:
Use only API classification SM with the words "ENERGY
CONSERVING" and the ILSAC Certification Mark (Starburst
Mark) displayed on the container.
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Engine oil capacity:
4.2 US qt (4.0 liters, 3.5 Imp qt)
225/45R17 235/45R17
17 7 JJ 17
2
33 psi (230 kPa, 2.3 kgf/cm )
2
32 psi (220 kPa, 2.2 kgf/cm )
2
60 psi (420 kPa, 4.2 kgf/cm )
245/40R18
1
8 JJ 18 8 / J
2
T135/70 D17