I have a 2008 chevy silverado crew cab 1/2 ton with the 5.3 active fuel management motor in it. Its been continuously burning oil (about two quarts every 3000 miles). So far, the gm mechanics have replaced pistons, rings, valves, valve seals, camshaft, lifters, and bearings. Everything that they have done hasn't reduced the oil consumption issue yet... Any ideas on what else is causing it? The truck now has 108000 miles on it, but the problem began at around 50k.