My car is a 2001 toyota corolla with 154000 miles on it. It has been burning about 2-3 quarts of oil every 600 miles. A mechanic recently replaced a valve cover gasket which was supposedly leaking oil. Three nights of delivering pizzas later the car has burned two more quarts of oil. What do I do???
first you need to do a compression and bleed down test to determine the cause of the oil consumption, (I take it you have checked for other leaks, such as a bad front crank seal, or a loose bolt on the pan ect.) You may just have failed valve guide seals, which is not an easy operation on an overhead cam engine, but not the end of the world either. Or you might have bad rings, or a bad head gasket. the compression test will tell you if you have any of these condtions. good luck.
I would look at the PCV valve first, if it was never serviced/replaced. Generally it is cheaper to replace than anything else.
If the condition persists, then to the compression and bleed down tests.