This bulletin is being revised to add models and model years. Please discard Corporate Bulletin Number 02-06-01-027A (Section 06 — Engine/Propulsion System). 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 accepted rate of oil consumption for the 6.6L Duramax™ Diesel engine is 0.946 liter (1 qt) within 379 liters (100 gallons) of fuel used. 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.

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