One of my buddies has the 4.7 in a dodge truck and he runs HDEO 15w40 in it year around here in NC. Im not saying this is smart or good or bad but he has done it for a long time and his truck is still running good. He does do mostly interstate driving though. He lives 30 miles from work almost all interstate so he is probably the best case for running a HDEO. He may not have had such good results if it was all short runs.