2003 CHEVROLET C/K Owners Manual

6-27
Engine Oil (Caterpillar

Diesel Engines)
See your Caterpillar
Operation & Maintenance Manual
for information on oil quality and viscosities as well as
the temperature range chart.
Engine Oil (DURAMAX Diesel)
Checking Engine Oil
It's a good idea to check your engine oil level every time
you get fuel.
The engine oil dipstick is
located in the engine
compartment on the driver's
side of the vehicle.
In order to get an accurate
reading, the oil must be
warm (at normal operating
temperature) and the vehicle
must be on level ground.Turn off the engine and give the oil at least five minutes
to drain back into the oil pan. With a cool engine, allow
30 minutes. If you don't, the oil dipstick might not show
the actual level.
Pull out the dipstick and clean it with a paper towel or a
cloth, then push it back in all the way. Remove it again,
keeping the tip down.

6-28 When to Add Engine Oil
If the oil is at or below the ADD line, then you'll need
to add at least one quart of oil. But you must use the
right kind. This part explains what kind of oil to use.
For engine oil crankcase capacity, see ªCapacities and
Specificationsº in the Index.
NOTICE:
Don't add too much oil. If your engine has so
much oil that the oil level gets above the proper
operating range, your engine could be damaged.
Be sure to fill it enough to put the level somewhere in
the proper operating range. Push the dipstick all the way
back in when you're through.
What Kind of Engine Oil to Use
Look for these two things:

CH
-4
Oils designated as API CH
-4 are best for your
vehicle. The CH
-4 designation may appear either
alone or in combination with other API designations,
such as API CH
-4/SJ or CH-4/CG-4/SJ.
These letters show American Petroleum Institute
(API) levels of quality.
NOTICE:
If you use oil that doesn't have this designation,
CH
-4, you can cause engine damage which is not
covered by your warranty.

6-29

SAE 15W-40
As shown in the viscosity chart, SAE 15W
-40 is
best for your vehicle. However, you can use SAE
10W
-30 at temperatures above 0F (-18C).
When it's very cold, below 0F (
-18C), you should
use SAE 5W
-40 to improve cold starting.
These numbers on the oil container show its
viscosity, or thickness. Do not use other viscosity
oils such as SAE 10W
-40 or SAE 20W-50.
This doughnut-shaped logo
(symbol) is used on most
oil containers to help you
select the correct oil. It
means that the oil has been
certified by the American
Petroleum Institute.
You should look for this on the oil container, and use
only those oils that display the logo.
GM Goodwrench
 oil of the recommended viscosity
grades meets all the requirements for your vehicle.

6-30 Engine Oil Additives
Don't add anything to your oil. The recommended oils
with the API service symbol are all you will need for
good performance and engine protection.
When to Change Engine Oil
Change engine oil and filter every 10,000 miles
(16 000 km) or every 12 months, whichever occurs first.
What to Do with Used Oil
Used engine oil contains certain elements that may be
unhealthy for your skin and could even cause cancer.
Don't let used oil stay on your skin for very long. Clean
your skin and nails with soap and water, or a good hand
cleaner. Wash or properly throw away clothing or rags
containing used engine oil. See the manufacturer's
warnings about the use and disposal of oil products.
Used oil can be a threat to the environment. If you
change your own oil, be sure to drain all the oil from
the filter before disposal. Never dispose of oil by putting
it in the trash, pouring it on the ground, into sewers, or
into streams or bodies of water. Instead, recycle it by
taking it to a place that collects used oil. If you have a
problem properly disposing of your used oil, ask your
dealer, a service station or a local recycling center
for help.
Engine Air Cleaner/Filter
Refer to the Maintenance Schedule to determine when to
replace the engine air cleaner/filter. See ªScheduled
Maintenanceº in the Index.
The engine air cleaner/filter
is located in the center of
the engine compartment.
Your gasoline or diesel engine has a restriction indicator
that lets you know when the engine air cleaner/filter
needs to be serviced.

6-31
The restriction indicator
is located in the engine
compartment near the
engine air cleaner/filter,
on the passenger's side of
the vehicle.
When the yellow indicator reaches the red ring in the
sight glass, it's time to service the engine air
cleaner/filter.
After the engine air cleaner/filter is properly serviced,
the indicator can be reset by pressing the button on top
of the indicator.
CAUTION:
Gasoline Engines Only: Operating the engine
with the air cleaner/filter off can cause you or
others to be burned. The air cleaner not only
cleans the air, it stops flame if the engine
backfires. If it isn't there, and the engine
backfires, you could be burned. Don't drive with
it off, and be careful working on the engine with
the air cleaner/filter off.
NOTICE:
Gasoline Engines Only: If the air cleaner/filter is
off, a backfire can cause a damaging engine fire.
And, dirt can easily get into your engine, which
will damage it. Always have the air cleaner/filter
in place when you're driving.
Your vehicle may be equipped with an optional instrument
panel mounted air filter restriction indicator. See ªWarning
Lights, Gages and Indicatorsº in the Index.

6-32
Automatic Transmission Fluid
When to Check
A good time to have it checked is when the engine oil is
checked. See your Allison Automatic Transmission
Operator's Manual to find out when to change your
transmission fluid and filters.
How to Check and What to Use
The Allison Automatic Transmission Operator's Manual
that came with the vehicle shows how to check the
automatic transmission fluid and what fluid to use.
Automatic Transmission External Filter
Your automatic transmission filter requires periodic
replacement.
Consult the Allison Automatic Transmission
Operator's Manual that came with the vehicle for
proper change intervals.
Manual Transmission Fluid
Refer to the Maintenance Schedule to determine how
often to check the lubricant and when to change it. See
ªScheduled Maintenance Servicesº in the Index.
Refer to the Maintenance Schedule to determine what
kind of fluid to use. See ªRecommended Fluids and
Lubricantsº in the Index.
When to Check
A good time to have it checked is when the engine oil is
checked. See your Maintenance Schedule to find out
when to change your transmission fluid.

6-33 How to Check and What to Use
Check the fluid level only when your engine is off, the
vehicle is parked on a level place and the transmission is
cool enough for you to rest your fingers on the
transmission case.
Then, follow these steps:
1. Remove the filler plug.
2. Check to be sure that the lubricant level is up
to the bottom of the fill opening. On heavy duty
transmissions (an inch of oil level equals about
one gallon of fluid.)
3. If the fluid level is good, install the plug and be sure
it is fully seated. If the fluid level is low, add more
fluid as described in the next steps.
How to Add Fluid
Here's how to add fluid. Refer to the Maintenance
Schedule to determine the proper fluid to use. See
ªRecommended Fluids and Lubricantsº in the Index.
1. Remove the filler plug.
2. Add fluid at the filler plug hole. Add only enough
fluid to bring the fluid level up to the bottom of the
fill opening.
3. Install the filler plug. Be sure the plug is fully seated.

6-34
Rear Axle
When to Check and Change Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant and when to change it. See
ªScheduled Maintenance Servicesº in the Index.
How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.If the level is below the bottom of the filler plug hole,
you'll need to add some lubricant. Add enough lubricant
to raise the level to the bottom of the filler plug hole.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See ªRecommended Fluids and
Lubricantsº in the Index.
Rear Axle Shift Motor (Option)
When to Check and Change Fluid
If you have an optional air-shift two-speed, controlled
traction, or locking differential type rear axle, a good
time to check the fluid level in the axle shift motor is
when the rear axle lubricant is checked. Use refrigerant
oil (shift motor only).
How to Check Fluid
Remove the plug on the front plate of the axle shift
motor, add enough fluid to raise the level to the bottom
of the filler plug hole, then replace the plug.
What to Use
Refer to your Maintenance Schedule to determine what
kind of lubricant to use. See ªRecommended Fluids and
Lubricantsº in the Index.