In this work, a general f-theory viscosity model based on the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS) has been developed for the description of the viscosity behavior of the normal alkanes family (from methane to n-octadecane). This generalf-theory model has been shown to provide satisfactory results for the modeling of the viscosity of the normal alkanes as well as carbon dioxide and nitrogen over wide ranges of temperatures and up to 100 MPa. In addition, using simple mixing rules, an evaluation of the model performance has been carried out for several n-alkane and carbon dioxide + n-alkane mixtures over wide ranges of temperature and pressure. The chosen mixing rules provide good mixture viscosity prediction, close to or within experimental uncertainty, which is satisfactory for most applications (industrial and research). Further, the combination of the PC-SAFT EoS with the f-theory adds one more thermophysical property to the list of properties for which this model already delivers an improved representation, making the application potential for the PC-SAFT EoS even wider. (c) 2006 American Institute of Chemical Engineers.