Chevrolet 2003 Impala Owner's Manual page 272

As in the chart shown previously, if you have the
3400 V6 engine, SAE 5W-30 is the only viscosity grade
recommended for your vehicle. You should look for
and use only oils which have the API Starburst symbol
and which are also identified as SAE 5W-30. If you
cannot find such SAE 5W-30 oils, you can use an
SAE 1OW-30 oil which has the API Starburst symbol, if
it's going to be 0°F (-18°C) or above. Do not use
other viscosity grade oils, such as SAE 1OW-40 or
SAE 20W-50 under any conditions.
As shown in the following chart, if you have the 3800 V6
engine, SAE 1OW-30 is the viscosity grade
recommended for your vehicle. However, you can use
SAE 5W-30 if it's going to be colder than 60°F
(1 6°C) before your next oil change. When it's very cold,
colder than 0°F (-18"C), you should use an SAE 5W-30
oil. These numbers on an oil container show its
viscosity, or thickness. Do not use other viscosity grade
oils, such as SAE IOW-40 or SAE 20W-50 under any
conditions.
RECOMMENDED SAE VISCOSITY GRADE ENGINE OILS
FOR BEST FUEL ECONOMY AND COLD STARTING, SELECT THE LOWEST
SAE VISCOSITY GRADE OIL FOR THE EXPECTED TEMPERATURE RANGE.
~~~ ~ ~~ ~~~~~ ~ ~ ~ ~ ~
. .
HOT
WEATHER
"F
t
100-
+ 80,-
+
60
1 -
t
un
+
20
~
0 -
I
SAL 5W-30
LOOK
FOR T H I S
SYMBOL
8 -
SAE 1DW-30
PREFERRED
above 0°F
(-18T)
WEATHER
DO NOT USE SAE 2OW-50 OR ANY OTHER
GRADE
OIL NOT
RECOMMENDED
3800
(Code K) V6 Engine
5-1 9