BEYOND THE VIN
Excessive Engine Oil Consumption In Certain GM Trucks and SUVs

Problem: Some General Motors customers may comment on excessive engine oil consumption in certain 2006-2007 GM trucks and SUVs models equipped with 4.8L or 5.3L V8 engines (RPOs LR4, LM7, or L59), as specified below. The rate of oil consumption described may be around 0.946 liter (1 quart) of engine oil in 805 to 1125 km (500 to 700 mi) and usually occurs on low mileage engines.

Cause: This condition may be caused by a nick in one or more valve stems.

Correction: Do not replace the engine assembly. Instead, inspect for excessive oil consumption, then inspect all valve for damage and replace cylinder heads as needed. (Special Note - If one or more damaged valve stems are identified in one head, then both heads must be replaced.)

Excessive oil consumption in some GM trucks and SUVs may be caused by a nick in one or more valve stems. (Photo — General Motors)

Procedure:

1. Complete the current Service Information diagnosis for any symptoms found. (Refer to Corporate Bulletin Number 01-06-01-011F for Information on Engine Oil Consumption Guidelines.)
2. If excessive oil consumption has been verified, all of the valve stems need to be inspected for damage. One or more of the valve stems may be nicked.
3. After removing the valve cover, all of the rocker arms need to be loosened to assure the valves are closed.
4. Depending on the location, it is possible to see a nicked valve stem through the valve spring coil (a mirror and flashlight will be required). In some cases the valve spring may need to be removed. Examples of a nicked valve stem are shown above.
5. A valve stem nick can occur in any 360 degree area due to valve rotation, so each valve stem must be examined carefully.
6. If the engine oil consumption is excessive, and one or more nicked valve stems have been found, the cylinder heads will need to be replaced. (Please efer to Cylinder Head Replacement - Left Side and Cylinder Head Replacement - Right Side in Service Information.

OEM Note: 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.