For all you Oil Whizzes out there.I have a 03 2500HD with a 6.0 that is due for an oil change soon. I was planning on changing from a 10W-30 Synthetic to a Redline 5W-40 Synthetic as I really like the HT/HS numbers of the Redline Oil. I have read a lot of good stuff about the Redline so I thought I would give it a try. The outside temp ranges from about -1F to around +90F. Would I notice a difference in mileage with the 5W-40 as opposed to the 10W-30? Also, would there be a better high temp protection factor with the 5W-40. What would you folks recommend I use? Any info and opinions will be greatly appreciated.