The common diesel fuels are: 0#, -10#, -15#, -20#, -30#, and -35# for military use.
These markings are mainly for low-temperature production, minus 10 degrees plus -10 # oil, minus 20 degrees - plus # 20 oil, some special equipment, also need low-grade diesel, the lower the label the more expensive ( -35# is the most expensive. Under normal circumstances, we use 0# is enough. In the winter in the northeast, when the temperature is minus 20 degrees, 0# diesel will freeze ice, so when the temperature is low, only Add low oil.
In short, what type of diesel oil is suitable for small four-wheel tractors depends on the local temperature. If there is uncertainty, when buying a tractor, you can consult the manufacturer in detail.