This may come as a shock to some of you, because I'm not a big fan of 3k oil changes, but my next two intervals with my Firebird will be 3k each.
After much consideration, I've decided to drain out my 5w30 Schaeffer Oil at 3k, and then do a 3k run with 0w30 Castrol Formula SLX. I've just been too curious to see how this oil will work in this car, and the reasoning for such short intervals here is quite simple. I'm running out of time! By the time the end of October hits, our weather will turn sharply colder (especially the overnight temps) so I want to have the chance to see how the German Castrol does in this car under good temperatures. If I don't do it now, I'll have to wait until next year, and my curiosity is killing me!
I will now switch my mom's car over to 5w30 Schaeffer Oil, since I've got almost 19 quarts of it. My sister's car will most likely be sold in a few months, it's almost for sure now that she's moving out to Vancouver, as her fiancee just got an amazing job offer out there that is too good to pass up. So I'll only have one more UOA on 0w30 Castrol from her car. I've still got 12L of the stuff, so I didn't want it to go to waste, so it was either run it in my car or my mom's, and I figure my car needs the thicker oil more than hers does.
My plan is to run 10,000km (6200mi) intervals with the 0w30 (if the UOAs look ok) so things are in line right now since I put in the current batch of oil at 140,000km, and will do those two 5000km intervals in a row.
This in no way means I don't believe Schaeffer Oil is good, just that my LT1 engine could probably use a thicker oil than 10cst at 100c. I feel with it's higher mileage and looser clearances, it needs something closer to 12cst, maybe even thicker (13-14?) to truly protect it under the hard use I put it under. I sure wish Schaeffer Oil would come out with a 5w40 oil, something on the thinner side of a 40wt preferably.