Welcome Paula. There is a bulletin regarding this issue with GM. Here is a copy of the bulletin.
#07-06-01-007B: Excessive Engine Oil Consumption (Verify Condition, Inspect Valve Stems, Replace Cylinder Heads, If Necessary) - (Jul 18, 2008)
This bulletin is being revised to inform technicians that the old cylinder heads are no longer being requested/required to be sent back to WPC. Please discard Corporate Bulletin Number 07-06-01-007A (Section 06 - Engine/Propulsion).
Some customers may comment on excessive engine oil consumption. The rate of oil consumption described may usually be around 0.946 liter (1 quart) of engine oil in 805 to 1125 km (500 to 700 mi).
The engine oil consumption may be caused by a nick in the valve stem.
Important: If one or more damaged valves are identified in one head, BOTH heads should be replaced.
Don't Do This
Do NOT replace engine assembly or build up cylinder heads with SPO material.
Important: The completely built-up cylinder heads can be obtained from the Warranty Parts Center.
Complete the current SI diagnosis for any DTCs or symptoms found. Refer to Corporate Bulletin Number 01-06-01-011C for Information on Engine Oil Consumption Guidelines.
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.
After removing the valve cover, all the rocker arms need to be loosened to assure the valves are closed.
It is possible to see a nicked valve stem through the valve spring coil (a mirror and flashlight will be required), but in some cases the valve spring may need to be removed. Photos of a nicked valve stem are shown below.
A valve stem nick can be in any 360 degree area due to rotation, so each valve stem must be examined carefully.
If the engine oil consumption is excessive, and a nicked valve stem has been found, the cylinder heads will need to be replaced. The cylinder heads will be serviced as an assembly (the head will be complete with valves and springs) and shipped to the dealer by the Warranty Parts Center (WPC). The dealer will have to order the necessary parts/gaskets to complete the cylinder heads remove and replace. Refer to the Cylinder Head Replacement procedures in the applicable Engine Mechanical sub-section.