I have been scouring the forums and the internet. My manual states MS 12991 and (API SP). In this forum everyone is stating that thier manual says (API SN). I just purchased the truck a couple of weeks ago and I am trying to find the correct oil and plan ahead. I can't seem to find any oil that meets both of these criteria. Does anyone know of an oil/brand I could use. Has anyone else seen this in their manual and is this a recent update to the owner's manual? I am also new to the forums concept, I used to buy Chiltons manuals for every vehicle I owned, I studied them to learn more about my vehicles but I figured I would try a more technological route with this one. Thanks in advance for any help!