Subaru 2004 Impreza - Manual (Page 403)

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Maintenance and service
! Recommended grade and viscosity
under severe driving conditions
If the vehicle is used in desert areas, in areas with very
high temperatures, or used for heavy-duty applica-
tions such as towing a trailer, use of oil with the follow-
ing grade and viscosities is recommended.
API classification SL (or SJ):
SAE viscosity No.: 30, 40, 10W-50, 20W-40, 20W-50
! Synthetic oil
You can use synthetic engine oil that meets the same
requirements given for conventional engine oil. When
using synthetic oil, you must use oil of the same clas-
sification, viscosity and grade shown in this owner’s
manual, and must follow the oil and filter changing in-
tervals shown in the maintenance schedule.
Cooling system
Never attempt to remove the radiator cap until
the engine has been shut off and has cooled
down completely. Since the coolant is under
pressure, you may suffer serious burns from a
spray of boiling hot coolant when the cap is re-
moved.
" The cooling system has been filled at the fac-
tory with a high quality, corrosion-inhibiting,
year-around coolant which provides protection
against freezing down to –33 °F (–36°C). For
adding, use genuine SUBARU coolant or an
equivalent: a mixture of 50% soft water and 50%
ethylene-glycol basis coolant. Use of improper
coolants may result in corrosion in the cooling
system. It is important to maintain protection
against freezing and corrosion, even if freezing
temperatures are not expected. Never mix dif-
ferent kinds of coolant.
"
Do not splash the engine coolant over paint-