'95 F250 ECLB 4x4 ZF5, 71,000-ish miles. Running Shell Rotella-T Synthetic 5w40 in the crankcase. I'm debating whether to change the oil before an upcoming road trip or after. It has about 3000 miles on it now, and will have about 6000 on it after the trip. I S-WAGged that 5000 was a good OCI for this particular oil, but I'm wondering if I should push it to 6000, or go ahead and do it now at 3000 to be safe. It'll be mostly Interstate driving. Am I pushing my luck at 6000?