I only do dealer service at this point. So it’s 0x30W synthetic, I think. Due to the extreme mileage I change it at 5k intervals.
FWIW I always run Valvoline full synthetic and switch the vehicle over to 10w30 after 100,000 miles. We have as a family over 2,000,000 miles on GM Trucks. Never had a lifter failure. I have silenced several noisy lifters on used ones belonging to friends by switching them to the Valvoline program. Disable the AFM as others have said.
Also, you mentioned plug and wire change. Run it in the dark and check those. The LS plug wires can be problem prone out of the box. Especially look at the wire in cylinder #8.