Chevrolet 2001 Impala Owner's Manual page 303

As shown in the following chart, if you have the
-
3800 V6 engine, SAE 10W 30 is best for your vehicle.
-
However, you can use SAE 5W 30 if it's going to be
colder than 60 _ F (16 _ C) before your next oil change.
-
When it's very cold, you should use SAE 5W 30.
These numbers on an oil container show its viscosity,
or thickness. Do not use other viscosity oils, such
-
as SAE 20W 50.
3800 (Code K) V6 Engine
6-16