Valvoline Premium Blue Extreme 5W40 Napa Gold Filter no bypass oil filter S&B Cold Air Intake 7,591 miles on this sample This oil sample was 5W40, NOT 15W40. I'm thinking of running extended oil changes, but wanted some input on this. I typically change out the oil between 7,500-8,000 miles. I ran 15W40 dino oil in the last 3,900 miles and will send that off to Blackstone for testing. I've filled sump with Rotella T6 5W40. Any thoughts?