File in Section:
Bulletin No.:

Service Bulletin

Date:

16-NA-376
September, 2017

INFORMATION
Subject:

Information on Higher Than Expected Oil Consumption

Brand:

Model:

Chevrolet
GMC

Model Year:

VIN:

from

to

Silverado
2500-3500

2017

2018

Sierra
2500-3500

2017

2018

Involved Region or Country

from

Engine:

Transmission:

to
Equipped with
6.6L Diesel
Engine
(RPO L5P)

North America and Israel

Information on Engine Oil Consumption
Guidelines for the 6.6L Duramax Diesel
Engine
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 combustion process, part of
this oil layer is consumed. As a result, varying rates of
oil consumption are accepted as normal in all engines.

Oil Consumption
Oil usage has a direct relationship with the amount of
fuel used. The harder an engine works, the more fuel
and oil it will use. Therefore, oil usage as a factor of fuel
usage is a more accurate indicator of acceptable oil
consumption levels than vehicle mileage.
The maximum oil consumption for the 6.6L Duramax™
Diesel engine (RPO L5P) is 2.36 liters (2.5 qt) within
379 liters (100 gallons) of fuel used. For heavy towing
applications (9 mpg/26.1 L/100 km (Liters per 100
kilometers)), this correlates to a consumption of 2.61
liter (2.76 qt) per 1000 miles. This rate only applies to
vehicles under warranty, maintained in accordance with
the appropriate maintenance schedule, driven at legal
speeds and within design intent of the vehicle.
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.

turbocharger outlet pipe for signs of oil, indicating worn
turbocharger shaft bushings or seals. Inspect for oil
leakage into the engine coolant.

Improper Reading of the Oil Level
Indicator (Dipstick)
The vehicle must be parked on a level surface to obtain
accurate oil level readings. 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 15
minutes, 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.

Gasket and External Leaks

High Speed or High RPM Driving

Inspect the oil pans, engine covers, and the engine oil
cooler for leakage. Inspect the turbocharger oil lines
and fittings for signs of leakage. Inspect the

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.

Copyright 2017 General Motors LLC. All Rights Reserved.

Page 2

September, 2017

Bulletin No.: 16-NA-376

Towing or Heavy Usage

Measurement of Oil Consumption

Towing a trailer or hauling additional weight will
increase oil consumption. 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.

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 8000 km (5000 mi) and the oil has
been changed for the first time. During initial engine
break-in periods before the first oil change, oil
consumption may exceed 3.8 liters (4 quarts) or more
per 379 liters (100 gallons) of fuel used.
1. Verify that the engine has no external leaks. Repair
as necessary.
2. Begin oil consumption test after next regularly
scheduled oil and filter change. It is critical to make
sure that the new oil filter is tightened 1 to 1-1/4
turn after contact. Refer to Engine Oil and Oil Filter
Replacement in SI. Oil changes should not be
performed during the test.
3. Verify that the engine is at normal operating
temperature (see Owner's Manual or Service
Manual).
4. Park the vehicle on a level surface
5. Wait at least 15 minutes, after the engine is shut
off, before checking the oil level to make sure that
most of the oil has had time to drain back into the
crankcase.
6. 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.
7. Dealer should record the vehicle mileage, date and
engine hours at the start of the test on the form
included in this bulletin.
8. Ask the customer to verify and record the date,
odometer, oil level, fuel added, and engine hours,
each time the vehicle is fueled, following steps 3-5
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 possible. The dealer will add oil to
return the oil level to full. If the oil level remains
above the add mark, the customer should continue
to operate the vehicle and verify the engine oil
level until either the oil level drops to or below the
add mark or at least 4800 km (3000 mi) has
accumulated since the test began before returning
to the dealership for a final evaluation.
9. Refer to Oil Consumption section to compare the
final evaluation to the proper acceptable oil
consumption. Explain to the customer that their
engine meets the guidelines for oil consumption if it
falls into the acceptable range.

PTO Operation
Operation of a PTO will increase fuel and oil usage, as
the PTO driven accessory uses engine power to
operate.

Crankcase Ventilation System
Verify that the positive crankcase ventilation (PCV)
system is operating properly. Blockages, restrictions or
damage to the PCV system can result in increased
oil use.

Oil Dilution from Condensation
On vehicles that are usually driven short distances, less
than 8 km (5 mi), especially in colder weather,
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, 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
system 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.

Bulletin No.: 16-NA-376

September, 2017

Page 3

Oil Consumption Worksheet
Owner Name

Location

Dealer Name

Dealer Code

Assign TAC

TAC Case #

Engine Model

Serial #

VIN

Oil Brand

Oil Viscosity

Fuel Brand

DATE
Start
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29

ODOMETER
READING

ENGINE HOURS

FUEL QUANTITY
ADDED

OIL QUANTITY
ADDED

———————

———————

Page 4

September, 2017
ODOMETER
READING

DATE

Bulletin No.: 16-NA-376

ENGINE HOURS

FUEL QUANTITY
ADDED

OIL QUANTITY
ADDED

30
31
Total

Calculation:
=
System

Oil Used

/

Fuel Used

=

Qt/Gal or L/L

*

English

/

=

*

100

=

Metric

/

=

*

379

=

Version

2

Modified

Sept 7, 2017 – Added the 2018 Model Year.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

Oil Consumption
Qt/100 Gal
L/379L

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