I had a 2001 Silverado 6.0 and from new to 140,000 miles it used 1 quart of Mobil 1 every 3000 miles. Then at 140k the oil consumption doubled to 2 quarts every 3000 miles. No burning or leaks. Dealer said it could cost up to $1000 just to diagnose the problem. I got rid of it.
always had oil consumption problems when using Mobil 1. I haven't used it in a long time for that very reason.