Delo 400 15w-40? I ran it in mine last summer, seemed to work fine, but not really recommended. For the winter I've used 5w-30. My next change will be 10w-30. I'm using the larger than OE oil filter but just 6qts of oil. Good luck.
2004 Black X 4.0, auto, 3.73's, soft top 31-10.5-15 Toyo A/T's on 8" Ultra 175's, 2" Teraflex BB.