Abstract: A tractor hydraulic fluid composition is prepared from an isomerized base oil which: a) the product itself, its fraction, or feed originates from or is produced at some stage by isomerization of a waxy feed from a Fischer-Tropsch process (“Fischer-Tropsch derived base oils”); or b) made from a substantially paraffinic wax feed (“waxy feed”). In one embodiment, the tractor hydraulic fluid composition is characterized as having a reduced level of viscosity modifier in an amount of 0 to 10 wt. %, and a Brookfield viscosity at ?35° C. of less than 70,000 mPa.s.