On my last motor(not blown replaced for more power inseret Tim Allen grunt) I bought the car at 50K have no idea what the old owner used I got it from a dealer I then switched oils every so often. I would once a year do a short interval like 1K with whatever was cheapest usually WakMarts house brand, then if going on a long trip I would dump in some Synpower or Durablend, I really was hard on the thing too we are talking a 4.3L V8 moving a Caprice. When I took it out it was spotles inside, a friend that was over at the time was amazed, he has been into drag and circle track racing for longer than I have been alive and he said if he didn't trust me he would have sworn I had dropped the pan and cleaned it within the last 10K. I get more crap out of the bottom of my tranny pan than I did out of that oil pan. I can not say with any scientific explaination why it was so clean, but at the time I attributed it at least in part to the occasional short OCI with an off brand.
Don't worry though with the modded LT1 and the knowledge I have picked up here I am treating my motors better.