Looking at doing some PM on an '89 Chevy G30-based RV (TBI 350) that a friend just acquired. I've been running Schaeffer's 7000 10w30 in my '85 GMC (454) for about the last 10,000 miles (first OCI was 6,400) and am very pleased - it seems to hold up exceptionally well in the big, old, flat-tappet engine. But to save a bit in materials and have a more common oil when it comes to make-up, I'd feel just as good about using Rotella T5 or T6, probably in a 10w30 or 5w40 weight - not so much from prior experience with that oil as by reputation and the opinion of the BITOG collective. Any opinions yay/nay on either?