My brothers 2002 z71 with a 5.3L seems to be consuming a lot of oil. He said its not leaking out any where. I haven't checked it out yet. He said it was about 4 qts low a few days ago, and he keeps having to add in a lot of oil. He said sometimes when he starts up the truck black smoke will come out of the exhaust, which I thought black smoke means running rich, blue smoke means burning oil. Anyway, I know the pvc system on these motors will eat up a little bit of oil but not 4 qts in a few weeks. Any ideas whats going on here? He drives like there is no tomorrow, there are about 90k miles on it, and he has the transmission rebuilt twice, once with stock parts 2nd time with all upgraded parts lol.
List of mods: Nelson tune, 160* stat, long tubes, K&N cai, flowmaster muffler. I told him he needs to tone it down on his driving but he doesn't. I will check for any leaks next time I see the truck, but for now are there any ideas why it would be doing this, or the cause of it?

