The 6.0 liter is a very good engine. I would not worry or hesitate buying it provided you have the truck as a whole checked out.
oakbowery wrote:
I have a 2007 5.3 liter that I bought with 17k miles. It now has 130k miles. It has always used a quart of oil over the life of the oil change (3000 miles). I first thought something was wrong with it but it's always done it and still runs as strong as it did when I first bought it. Personally I wouldn't worry too much even if the 6.0 does use a little oil. It hasn't bothered my 5.3 yet.
I have an '08 5.3 that just turned 100k, ditto on oil consumption. Pretty much every small block GM V8 I've ever owned has had some oil consumption.