Just did an OCI on my Sierra, draining the PP 10-30 after 7000+ miles and going back to the Golden Elixir Of The Gods, with an order of SLOB on the side.
That's 6 qts out of my inventory, 18 qts to go. If I can do an 8000 mile OCI, I could get to about 95,000 miles on my truck before the GC...