Boxster racers and hpde folks: what oil do you run and how often do you change it?

[j.fro]

in my autocross car (7500-10k yearly, 15-20 events) I change every 5000 miles. In the summer I use Castrol Edge 10W-40. In the winter I go to 0W-40. A sample goes to Blackstone labs for analysis with each oil change. Same goes for my 996 daily driver ( 30k yearly) but interval goes to 7500 miles and I do analysis every other change.