thats funny, i have a 2001 2500hd with the vortec 8.1 and it always has used oil!! its got a little over 204,xxx mi. and its still a strong runnin truck!!
and the guy is right about seeing your oil level creep up the dipstick.... youll get some fuel over in the oil between changes.... i monitor my oil levels from time to time.
You know, I LOVED my 8.1.
Honestly, if GM would still put it in a one ton, I would have bought one in a heartbeat.
I sell mine off at 100K, so the added expense of the diesel doesn't really pay for me.
That being said, my new truck is definitely a lot nicer than my last!