Selective re-extraction of lube extracts to reduce mutagenicity index

A selective extraction process for producing a high yield of aromatics-rich process oil extract having a low Mutagenicity Index and low concentration of polycyclic aromatics (PCA) from a feedstock comprising the distillate aromatic extract (DAE) recovered from the first extraction solvent of a lubricating oil solvent refining process, said extraction process comprising:

• contacting the DAE with a second extraction solvent in a second extraction zone at a temperature from 0.degree. C. to 100.degree. C. for a time sufficient to selectively extract the polycyclic aromatics from the DAE and form a two phase extraction mixture, in which the second solvent comprises dimethylsulfoxide, sulfolane and propylene carbonate and has a higher dielectric constant of at least 44 at 25.degree. C. compared to the first extraction solvent;
• separating the second extraction zone extraction mixture and recovering a raffinate comprising the aromatics-rich process oil in at least a 70 weight percent yield, in which the aromatics-rich process oil contains not more than 3.0 weight percent PCA and exhibits a Mutagenicity Index of not more than 1.0.