GM Service Manual Online
For 1990-2009 cars only

Excessive oil consumption, not due to leaks, is the use of 0.9 L (1 qt) or greater of engine oil within 3 200 kilometers (2,000 miles). The causes of excessive oil consumption include the following conditions:

    â€¢ External oil leaks--Tighten bolts and/or replace gaskets and oil seals as necessary. Refer to Oil Leak Diagnosis.
    â€¢ Incorrect oil level or improper reading of oil level indicator--With the vehicle on a level surface, allow adequate drain down time and inspect for the correct oil level.
    â€¢ Improper oil viscosity--Use recommended SAE viscosity for the prevailing temperatures.
    â€¢ Continuous high speed driving and/or severe usage
    â€¢ Crankcase ventilation system restrictions or malfunctioning components
    â€¢ Oil residue in the charge air cooler system is normal with a closed PCV system
    â€¢ Valve guides and/or valve stem oil seals worn, or the seal omitted--Ream guides and install oversize service valves and/or new valve stem oil seals.
    â€¢ Piston rings broken, improperly installed, worn, or not seated properly--Allow adequate time for rings to seat. Replace broken or worn rings, as necessary.
    â€¢ Piston improperly installed or misfitted