Five vacuum residues from different Mexican refineries have been fractionated into their four principal components: saturates, aromatics, resins, and asphaltenes, commonly known as SARA fractions. The determinations were made by means of the chromatographic separation technique, using a variation of the standard method ASTM D4124-01. The present article is focused on the effect of SARA fractions, mainly the asphaltenes, aromatics and saturates on the viscosity of the vacuum residues. The results show how the characteristics of the vacuum residues are different due to the origin of the blends of crude produced in the different regions of Mexico. According to the obtained results, it is possible to discern how the viscosity increases as the asphaltene content increases and aromatics and mainly saturates decreases, varying from 3,000 cP for 18% of asphaltenes and 11% of saturates to 50,000 cP for 26.8% of asphaltenes and 8.4% of saturates.