The main objective of this article is to demonstrate by experimental measurements the capability of the quartz crystal resonator (QCR) to characterize samples of liquor at different concentrations of adulteration with methanol, classify them according to their viscosity, and identify how to use this capability as a potential detection of fake liquor. According to the literature, the fake liquor is a common problem detected in several countries across the globe. The current strategy to detect the fake liquor is based on a piezoelectric biosensor that permits the classification of the samples according to its viscosity. The viscosity is a useful variable to determinate the degree of adulteration in the liquor samples because the viscosity value between ethanol (straight liquor) and methanol (most common fake liquor) is very different.