|
 .
| |
|
Subject:
Information on Engine Oil Consumption Guidelines
Models: All 1996-2001 Passenger Cars and Gasoline Powered Light Duty
Trucks
Under 8500 LB GVW.
NOTE: This bulletin is being revised to add Model Years 2000 and
2001.
Please discard Corporate Bulletin Number 76-60-04A.
All engines require oil to lubricate and protect the load bearing and
internal moving parts from wear including cylinder walls, pistons and
piston
rings. When a piston moves down its cylinder, a thin film of oil is
left on
the cylinder wall. During the power stroke, part of this oil layer
is
consumed in the combustion process. As a result, varying rates of
oil
consumption are accepted as normal in all engines.
Oil Consumption
The accepted rate of oil consumption for engines used in the vehicles
referenced is 0.946 liter (1qt) in 3200km (2000 mi). This rate only
applies
to personal use vehicles, under warranty, maintained in accordance with
the
appropriate maintenance schedule, with less than 58,000km (36,000 mi), or
80,450 km (50,000 mi) for Cadillac, driven at legal speeds in an unloaded
(for trucks) condition.
Many factors can affect an owner's concern with oil consumption.
Driving
habits and vehicle maintenance vary from owner to owner. Thoroughly
evaluate each case before deciding whether the vehicle in question has
abnormal engine oil consumption.
Gasket and external Leaks
Inspect the oil pan and engine covers for leakage due to over-tightened,
damaged, or out of place gaskets. Inspect oil lines and fittings for
signs
of leakage.
Improper Reading of the Oil Level Indicator (Dipstick)
Verify that the dipstick tube is fully seated in the block. When
checking
the oil level, make sure the dipstick is wiped clean before taking an oil
level reading and fully depress the dipstick until the shoulder bottoms
out
on the dipstick tube. The dipstick should be the proper part number
for the
engine/vehicle that is being checked.
Not Waiting Long Enough After Running Engine to Check Oil Level
The vehicle should be allowed to sit for at least 5 minutes (20 minutes
for
the 2.4 L LQ1), after the engine has been shut off, before taking an oil
level reading to assure the oil has had enough time to drain back into the
crankcase. In order to ensure accurate results, the temperature of
the oil
should be close to the same temperature as the last time the oil level was
checked.
Improper Oil Fill After an Oil Change
Following an oil change, verify that the proper amount and type of oil was
put in the engine and that the oil level on the dipstick is not above the
full mark or below the add marks. Refer to the Owner's Manual or
Service
Manual for information on recommended oil quantity, viscosity, and
quality.
High Speed or High RPM Driving
Continuous driving at high speeds/high RPMs may increase oil consumption.
Because this may not always be an everyday occurrence, it is hard to
determine exactly how much the oil economy will be affected.
Towing or Heavy Usage
Towing a trailer will increase oil consumption and may cause oil
consumption
to fall below the normal accepted rate referenced in this bulletin for an
unloaded vehicle in a personal use application. Large frontal area
trailers
will further increase the work required from the engine, especially at
highway speeds, and thus increases the rate of oil consumption.
Crankcase Ventilation System
Verify that the positive crankcase ventilation (PCV) system is operating
properly. Incorrect PCV valves, blockages, restrictions, or damage
to the
PAC system can result in increased oil use.
Oil Dilution (Fuel and Water)
On vehicles that are usually driven short distances, less than 8 km (5
mi),
especially in colder weather, unburned fuel and condensation generated
from
cold engine operation may not get hot enough to evaporate out of the oil.
When this occurs, the dipstick may indicate that the oil level is
over-full.
Subsequent driving on a trip of sufficient length to enable normal engine
operating temperature for 30 minutes or more, in order to vaporize excess
moisture and fuel, may give the customer the impression of excessive oil
consumption.
Engine Temperature
If an engine is run at overheated temperatures (see Owner's Manual or
Service Manual) for more than brief periods, oil will oxidize at a faster
than normal rate. In addition, gaskets may distort, piston rings may
stick,
and excessive wear may result. Verify that all cooling systems
components
are in proper working order.
Engine Wear
Piston scuffing, excessive piston-to-wall clearance, tapered or out of
round
cylinders, worn, damaged or improperly installed valve guides, seals and
piston rings will all cause an increase in oil consumption.
Measurement of Oil Consumption
Engines require a period of time to BREAK IN so that moving parts are
properly seated. Therefore, oil economy should not be tested until
the
vehicle has accumulated at least 6400 km (4000 mi). An exception
would be
allowed only if an engine is reported to be using more than 0.946 liter (1
qt) in 1600 km (1000 mi).
1. Verify that the engine has no external leaks. Repair as
necessary.
2. Verify that the engine is at normal operating temperature (see
Owner's
Manual or Service Manual).
3. Park the vehicle on a level surface.
4. Wait at least 5 minutes (20 minutes for the 3.4 L LQ1), after the
engine
is shut off, before checking the oil level to make sure most of the oil
has
had time to drain back into the crankcase.
5. Verify that the oil level is at, but not above, the full mark on
the
dipstick, and that the proper viscosity and quality oil are being used as
recommended in the Owner's Manual.
6. Record the vehicle mileage, date, and exact oil level on the form
included in this bulletin.
7. Ask the customer to verify the oil level, each time the vehicle
is
fueled, following steps 1-6 and return the vehicle to the dealership if
the
oil level is found at or below the add mark, 0.946 liter (1 qt) low.
If the
oil level remains above the add mark, the customer should continue to
operate the vehicle and verify the engine oil level until 3200 km (2000
mi)
has accumulated before returning to the dealership for a final evaluation.
8. If the final evaluation shows that the engine uses more than
0.946 liter
(1qt) in 3200 km (2000 mi), follow the published symptom diagnostics as
described in the appropriate Service Manual. If the oil consumption
test
shows that the engine uses less than 0.946 liter (1 qt) in 3200 km
(2000mi),
explain to the customer that their engine meets the guidelines for oil
consumption. |
|
