I've been sending my oil (Pennzoil Ultra Full Synthetic) out to Blackstone for testing (bought a 6-pack). My plan is to use Full Synthetic 5W20 oil and change it every 6 months, which is about every 7,500 to 8,000 miles based on my driving.
The first was at 8,330 miles with 5,120 on the oil . They noticed wear-in materials (i.e. copper and silicon), but that was expected. They said I was fine to go 7,500 miles.
SUS Viscosity @ 210°F - 53.4
cSt Viscosity @ 100°C - 8.29
TBN - 4.0
The second was at 16,833 miles with 8,503 on the oil. They noticed a lower level of residual wear-in materials and said that I would be fine going 10,000 miles.
SUS Viscosity @ 210°F - 54.1
cSt Viscosity @ 100°C - 8.52
TBN - 3.1
One of these days I'll stop being lazy and post the full reports.
Note: Mine isn't an SRT. I have a V6 Limited so the oil characteristics may be different.