Bulletin No.: 16-NA-376

Service Bulletin

Date: December, 2024

INFORMATION
Subject:
Brand:

Chevrolet

GMC

Information on Higher Than Expected Oil Consumption
Model:

Model Year:
from

to

Silverado

2017

2018

Silverado 2500/3500

2019

2025

Silverado 4500HD,
5500HD, 6500HD

2019

2025

Sierra

2017

2018

Sierra 2500/3500

2019

2025

Involved Region or Country

VIN:
from

Engine:
to

Transmissi
on:

Equipped with 6.6L
Diesel Engine (RPO
L5P or L5D)

North America, Middle East, Israel, South America and Thailand.

Important: Service agents must comply with all International, Federal, State, Provincial, and/or Local laws
applicable to the activities it performs under this bulletin, including but not limited to handling, deploying,
preparing, classifying, packaging, marking, labeling, and shipping dangerous goods. In the event of a
conflict between the procedures set forth in this bulletin and the laws that apply to your dealership, you
must follow those applicable laws.

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 or L5D) is 2.0 liters (2.0 qt) within
321 liters (80 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 2.0 liter (2.0 qt) per 1233 Km (766 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.

Copyright 2024 General Motors. All Rights Reserved.

Page 2

December, 2024

Bulletin No.: 16-NA-376

Gasket and External Leaks
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 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.

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 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.

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

December, 2024

Page 3

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 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.

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

ODOMETER
READING

ENGINE HOURS

FUEL QUANTITY
ADDED

OIL QUANTITY
ADDED

———————

———————

Page 4

December, 2024
DATE

Bulletin No.: 16-NA-376

ODOMETER
READING

ENGINE HOURS

FUEL QUANTITY
ADDED

OIL QUANTITY
ADDED

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
30
31
Total

Calculation:
System

Oil Used

/

Fuel Used

=

Qt/Gal or L/L

*

=

Oil Consumption
Qt/100 Gal
L/379L

English

/

=

*

100

=

Metric

/

=

*

379

=

Bulletin No.: 16-NA-376

December, 2024

Page 5

Version

9

Modified

Released November 15, 2016
Revised September 07, 2017 – Added the 2018 Model Year.
Revised July 20, 2018 – Added the 2019 Model Year.
Revised June 26, 2019 – Added 2019 and 2020 Model Years to 2500/3500 Models.
Revised October 22, 2020 – Added 2021 Model Years to 2500/3500 Models, Added
2019–2021 Silverado 4500, 5500 and 6500 HD Models, and added RPO L5D.
Revised September 08, 2022 – Added 2022 and 2023 Model Years.
Revised March 13, 2023 – Added 2024 Model Year to 2500/3500 Models.
Revised August 09, 2024 - Added 2025 to Model Year.
Revised December 10, 2024 - Updated Oil Consumption section.

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.

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