Stratiev D.S.Nenov S.Shishkova I.K.Dinkov R.K.Zlatanov K.Yordanov D.Sotirov S.Sotirova E.Atanassova V.Atanassov K.Stratiev D.D.Todorova‐yankova L.2024-07-102024-07-102024-07-102024-07-102021-08-012079-927610.3390/resources10080082SCOPUS_ID:85112751878https://rlib.uctm.edu/handle/123456789/664This work presents characterization data and viscosity of 34 secondary vacuum gas oils (H‐Oil gas oils, visbreaker gas oils, and fluid catalytic cracking slurry oils) with aromatic content reaching up to 100 wt.%. Inter‐criteria analysis was employed to define the secondary VGO charac-teristic parameters which have an effect on viscosity. Seven published empirical models to predict viscosity of the secondary vacuum gas oils were examined for their prediction ability. The empirical model of Aboul‐Seud and Moharam was found to have the lowest error of prediction. A modifica-tion of Aboul‐Seoud and Moharam model by separating the power terms accounting for the effects of specific gravity and average boiling point improves the accuracy of viscosity prediction. It was discovered that the relation of slope of viscosity decrease with temperature enhancement for the secondary vacuum gas oil is not a constant. This slope increases with the average boiling point and the specific gravity augmentation, a fact that has not been discussed before.enArticle