The climate is mild SoCal. How does 5W-40 Rotella Synth do at 60F? Is it still thinner than a 10W-30? I'm thinking that a high TBN oil with good flow on startup is what I need.
5w-40 Rotella is most likely going to be slightly thicker at 60 F, but it is still a great oil for the 4.3L. You really have no worries what so ever about cold flow in southern California. 20w-50 would flow fine at those temps.