Others might disagree, but if I were you I'd change out that oil to a high quality full synthetic tomorrow (or asap), before your next trip. Even if it's not redline which is my goto at the moment, something good. For a start your current oil is probably on the way out anyway (anything above 250 is bad news for standard oil), and this would be a great test to see if a different/better oil helps mitigate this kind of problem, it's great real world testing with no marketing spin or agenda being pushed by somebody. I'd prefer a 5w-30 but would understand if you don't want to go that far.
In fact, if you wanted to run this test, i'd be happy to paypal you $50 to put towards it? I'd just need your forum username printed on a paper next to the dealer receipt and include a screenshot of the temps of your next trip on that oil as some sort of proof I guess. Honestly, this type of feedback would be invaluable to me and I'm sure to many other forum members.