When I get around to it, I'll post a UOA on my daughter's 2000 RS. Fuel was at 2% due to 1 mile trips to high school and daily short trips around town. The oil, Havoline 5W30, sheared to 54.9 SUS (a 20 weight) in 3,600 miles.
Even with 2% fuel dilution on GC, it remained a very thick 30 weight so thicker oils do tolerate fuel dilution better. Plus GC has elves in it.