My wife drives a '09 LTZ 1/2 ton and with the 5.3 active fuel mangement (AFM) and it began using oil at around 50,000 miles. Did some reading online and found that to keep the the AFM from coming on you can drive in manual mode and keep it in 5th  gear. The oil use all but quit. Mileage dropped some too, though. However, now the engine is making noise now and after talking to the dealer they're going to replace the camshaft. This is the third one they've done like this. It goes in tuesday so we'll see what they find. I'm disapointed, the older 5.3 engines had great reputation around here.