Production of non-carcinogenic brightstock extracts

A method for producing a brightstock extract, the method comprising:

• selecting a distillation cut point temperature between a resid fraction and one or more distillate fractions, the distillation cut point temperature corresponding to a mutagenicity index value of 0.5 or less for a brightstock extract formed from the resid fraction, the distillation cut point temperature being based on,
• (a) a first correlation between a fractional weight boiling temperature for a vacuum resid fraction and a distillation cut point temperature for separating the vacuum resid fraction from a feedstock,
• (b) a second correlation 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, wherein the second correlation has a linear correlation slope of 0.90 or less, and
• (c) a third correlation between the fractional weight boiling temperature for the brightstock extract and a mutagenicity index value;
• distilling a feedstock to separate one or more distillate fractions from a resid fraction at the selected distillation cut point temperature;
• passing at least a portion of the separated resid fraction through a deasphalting unit to produce at least a deasphalted oil fraction;
• and
• passing the deasphalted oil fraction through a solvent extraction unit to produce at least a brightstock extract having a mutagenicity index value of 0.5 or less.