Abstract: Viscosity has been identified as the main solution property in polymer flooding applications. Currently UTCHEM simulator is claimed to be more robust than CMG-STARS and ECLIPSE, since it takes into account salinity and hardness effects on polymer viscosity other than polymer concentration and shear rate effects. However, UTCHEM model was developed using One-Factor-at-A-Time (OFAT) approach. The major disadvantage of the OFAT strategy is that it fails to consider any possible interactions between the factors. In this research, it has been showed that interactions between factors in polymer studies are very common and they lead to producing poor results by OFAT strategy and consequently by the viscosity model. This study evaluates the viscosity model of UTCHEM simulator for predicting bulk viscometric data. UTCHEM Model was compared to experimental data to evaluate its predictive accuracy. Although, UTCHEM Model accurately predicted polymer viscosity at zero shear rate, it gave inaccurate results at increased shear rate. Results showed that there exist interaction among the various factors involved in polymer studies. Consequently, Design Of Experiment (DOE) is proposed for improved model for predicting polymer viscosity.