slant 6 oil weight

Been running store brand 10w30 till I got the kinks worked out.Now that she's running well, changed it and used Valvoline Max Life 10w40. Oil pressure went up 5psi at startup and holds at 40+ cruising and 10+ at idle. Before she'd be lucky to hold 35psi at cruising and 5 at idle. Valves need adjusting but runs quieter too. She definetly like the heavier, higher grade oil. Lot of miles on her so I don't expect much.