Just got the report back from my oil experiment. I ran a mix of 50/50 Redline 40W race and 5W-30 street oil. I added two quarts of Castrol Syntec during the 8200 miles because I didn't have anything else. Anyway, I was concerned that since the race oil has very little detergent qualities that running that long might have been a problem. Test came back good. I'll probably change this oil at closer to 7k miles just because that's my typical interval.