Carlton, I really do hope that you can get a definitive answer for us from your folks at the Cummins factory about the type of oil that is used to fill the engine when it leaves the factory. I try not to be overly neurotic about things like this, but, on the other hand, I strive to keep my tools, cars, Harley, truck and other assorted toys in good repair, well maintained and serviced. I read the owners manuals, get the required service in a timely fashion and used the right parts and lubricants. And, as I said in one of my prior threads, I thought I had this Dodge Cummins lubricant thing down until you posted your reply saying they left the factory with Premium Blue Extreme synthetic oil in them. And, I guess, in the long run, whatever oil it has might not make that big of a difference, but I, and I believe several other members of this forum, would just like to try and get the best oil, parts, and service for our trucks so that they can run long and hard. And there certainly seems to be lots of misinformation about which oil to use in the Cummins engine. Thanks.