ND, try whatever you think is best based on the chart, but I think that unless you use full synthetic 10w-30, you will find that 10w-30 is still a little heavy for the winter if your tractor sits in an unheated space. Based on my own experience of almost 30 years of having 3 similar tractors stored both in and outside of heated spaces, I found that it took 15 seconds or more just for the oil light to go out if the barn wasn't heated. This essentially means no new oil was getting up to the upper portion of the engine during that time. Oil on the NHs must travel up a very small tube on the outside of the engine (right side, about midway back) to get to the upper portions and the pressure sender. Maybe not a big deal, but not what I wanted to see. When I switched to 5w-40, the problem went away. Easy cranking and the light went out in a second or two. IMHO, I definetely would not use 15w-anything in the winter in ND in a TC-series, heater storage or not.
