The invention provides a process for preparing a fluid having a boiling point in the range of from 150 to 260° C. and comprising more than 80% by weight of isoparaffins and less than 50 ppm of aromatics, comprising the step of catalytically hydrogenating a feed comprising more than 85% by weight of oligomerized olefins, at a temperature from 115 to 195° C. and at a pressure from 30 to 70 bars. The invention also provides the fluid obtainable by the process of the invention and the use of said fluid.