Viscosity reduction of crude oil for its efficient transportation through cross country pipelines is of prime importance in the petroleum industry. One of the methods is to blend the crude oil with light hydrocarbons and organic solvents. The method is easy to implement and is widely used for transporting heavy crude oils and bitumen. A number of diluents like condensates, light oils, naphtha, middle distillates and organic solvents are used. The resultant viscosity depends on number of factors like the compositionof crude oil, properties ofdiluent, oil/diluent ratio and the interaction between crude oil and the diluent. This requires a good mathematical model for accurate viscosity prediction. A number of models available in the literature have been discussed in this paper. Also an empirical model based on experimentationfor viscosity reduction of crude oil diluted withn-hexane at different temperatureshas been developed. The model gives fair accuracy in a limited operating range