I am second guessing myself on choice of oil for the "winter".
I live and work in the Winston Salem, NC area. We are new to the state, having moved here from San Antonio, TX. I purchased the truck upon moving here; it has 1 previous owner and he is local to Winston Salem.
I ended up using 10w-30 Mobil oil in my truck. I don't pull anything with it and I thought I would be driving up to Michigan a few times this winter with it, but I am not. I am not used to the winters in this area and have no idea what to expect as far as temp ranges. Should I change the oil back to 15w-40? I dont want to use synthetic yet.
I'd wait for fuzzy to chime in he is the diesel guy around here.
My non-diesel opinion would be to put what the manual suggests. It just doesn't get all that cold around here. A little colder where you are then here in the triangle but not much. Nothing like up north/mid-west.
For the Winston area the average low in January is 25f. The average High in July is 87f.
I'm not a fan of full synthetic regardless of engine or climate.
Yeah, the ford manual says 30F and above, use 15w-40 and 30F and below use 10w-30. We seem to ride the line here in Winston. Was 27F this morning. I used to live in northern Minnesota and it was -20's and -30's regularly Dec - Feb... I didnt have a diesel and I mostly drove my snowmobile to work anyways!!
I leave 15w-40 in my "old school diesel"(with 190,000 on the clock) year-round. The 10w-30 will be better for start ups. The problem is the really warm days we get this time of the year. Fri 67, Sat 70. I think my son used the Motorcraft synthetic blend in his 6.0 .