Higher Than Expected Oil Consumption – 2017-2023 Chevrolet Silverado & GMC Sierra

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Copyright 2022 General Motors LLC. All Rights Reserved. Service Bulletin Bulletin No.: 16-NA-376 Date: September, 2022 INFORMATION Subject: Information on Higher Than Expected Oil Consumption Brand: Model: Model Year: VIN: Engine: Transmission: from to from to Chevrolet Silverado 2017 2018 Equipped with 6.6L Diesel Engine (RPO L5P or L5D) Silverado 2500/3500 2019 2023 Silverado 4500HD, 5500HD, 6500HD 2019 2023 GMC Sierra 2017 2018 Sierra 2500/3500 2019 2023 Involved Region or Country North America, Middle East, Israel, South America and Thailand. 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 2.36 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. 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. Page 2 September, 2022 Bulletin No.: 16-NA-376 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. 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. Bulletin No.: 16-NA-376 September, 2022 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 ODOMETER READING ENGINE HOURS FUEL QUANTITY ADDED OIL QUANTITY ADDED 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 Page 4 September, 2022 Bulletin No.: 16-NA-376 DATE ODOMETER READING ENGINE HOURS FUEL QUANTITY ADDED OIL QUANTITY ADDED 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 = Version 6 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. 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. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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