The present invention is a method and apparatus for determining oil based mud contamination of a hydrocarbon fluid obtained from a wellbore during a formation testing. The invention includes receiving a model for simulating the contamination and receiving an empirical equation for computing the contamination. At a given pumping time, a simulated contamination is generated based on the model and an empirically computed contamination is generated based on the first empirical equation. The simulated contamination and empirically computed contamination are compared and a determination as to which is more reliable is made. Revision of the first model or first empirical equation based is then performed.