Provided are multiple correlations for relationships between MI value for a brightstock extract and the distillation cut point temperature used for separation of the vacuum resid that is used to form the brightstock extract. Based on these correlations, a BSE having a desired MI value can be formed based on an adjustment of the distillation cut point temperature. A first correlation establishes a relationship between a fractional weight boiling temperature for a vacuum resid fraction and a distillation cut point temperature for separating the vacuum resid fraction from at least one distillate fraction in a feedstock. A second correlation establishes a relationship between a fractional weight boiling temperature for a brightstock extract derived from the vacuum resid fraction, and the fractional weight boiling temperature for the vacuum resid fraction. A third correlation has been established between the fractional weight boiling temperature for the brightstock extract and a mutagenicity index value.