I've got just under 3k on my LZ0 and it's hard to tell what it's doing because I changed the oil at 500, 1500, and getting ready to do it again. The next interval will span 2k miles before probably going to a max of 3500 -- but using the recommended 0w20. Some superstition, and some data, I don't want to do longer intervals for the real or perceived possibility of the oil losing viscosity with longer use, starting from only 20 weight oil. I use Mobil 1 ESPx2.
In the last 1500 miles most of it has been higher speed, highway driving 70mph+, and only a little towing. I topped off the oil at about 2750 miles, adding about 1/8 quart to put the level back on full. IMO, nothing to worry about.
There's still a possibility a defective thrust bearing could take out the whole engine before 10k or so. That's a lovely thought to ponder, but if it happens, I'll get the engine replaced and send the truck down the road and find something else.