A process for converting light paraffins to heavier paraffinic hydrocarbon fluids is disclosed. The process involves: (1) oxidation of iso-paraffins to alkyl hydroperoxides and alcohols; (2) conversion of the alkyl hydroperoxides and alcohols to dialkyl peroxides; and (3) radical-initiated coupling of paraffins and/or iso-paraffins using the dialkyl peroxides as radical initiators, thereby forming heavier hydrocarbon products. Fractionation of the heavy hydrocarbon products can then be used to isolate fractions for use as hydrocarbon fluids.