Chevrolet 2003 Astro Owner's Manual page 235

As in the chart shown previously, 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 IOW-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.
Notice: Use only engine oil with the American
Petroleum Institute Certified For Gasoline Engines
starburst symbol. Failure to use the recommended
oil can result in engine damage not covered by
your warranty.
GM Goodwrench@ oil meets all the requirements for
your vehicle.
If you are in an area of extreme cold, where the
temperature falls below -20°F (-29"C), it is
recommended that you use either an SAE 5W-30
synthetic oil or an SAE OW-30 oil. Both will provide
easier cold starting and better protection for your engine
at extremely low temperatures.
Engine Oil Additives
Don't add anything to your oil. The recommended oils
with the starburst symbol are all you will need for
good performance and engine protection.
When to Change Engine Oil
If any one of these are true for you, use the short
tripkity maintenance schedule:
e
e
e
Most trips are less than 5 miles (8 km). This is
particularly important when outside temperatures
are below freezing.
Most trips include extensive idling (such as frequent
driving in stop-and-go traffic).
You frequently tow a trailer or use a carrier on top
of your vehicle.
The vehicle is used for delivery service, police, taxi
or other commercial application.
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