The Shop Should have Done a Leakdown Test (WARM) for a Proper Diagnosis....If They OVERLOOKED a defective ring the Valve Job Would Not have Cured the Oil Consumption !
I Have Tried Using ATF on Gummed Up Rings and Have Seen Good Results With Using a Quart of ATF at the Next Oil change Then Dump it it 500/800 miles
Then Try The Mobil One
How many Miles on Your car?
Is The Car Using a Quart in 500 Miles?