That is a lot of oil consumption. A couple of things can cause this level of oil burning. Stuck piston rings from oil related residue build up binding the rings together. Heavy sludge in the heads causing the drain holes to be constricted, whereby the oil is getting pumped up to the top of the motor faster than it can gravity feed back down to the oil pan. Or the third could be worn or dirty valve stem seals.
I would recommend that you run the Fast Track method for sludge. That would entail adding two bottles of Auto-Rx as part of a fresh oil change. Then operate the car as you normally would for 2000 miles, topping off the oil as needed. I highly recommend inspecting or replacing the PCV valve before you start. A sticky or stuck PCV valve will trap possitive pressure inside the oiling system and cause excess oil burning as well as sludge formation.
