Abstract: The present invention relates to a process for preparing a residual base oil from a hydrocarbon feed which is derived from a Fischer-Tropsch process, the process comprises the steps of: (a) providing a hydrocarbon feed which is derived from a Fischer-Tropsch process; (b) subjecting the hydrocarbon feed of step (a) to a hydrocracking/hydroisomerisation step to obtain an at least partially isomerised product; (c) separating at least part of the at least partially isomerised product as obtained in step (b) into one or more lower boiling fractions and a hydrowax residue fraction; (d) catalytic dewaxing of the hydrowax residue fraction of step (c) to obtain a highly isomerised product; (e) separating the highly isomerised product of step (d) into one or more light fractions and a isomerised residual fraction; (f) mixing of the isomerised residual fraction of step (e) with a diluent to obtain a diluted isomerised residual fraction; (g) cooling the diluted isomerised residual fraction of step (f) to a temperature be