Patent ID: 7601253

Claim:
A process oil comprising, in a mixing ratio of 95/5 to 5/95 (extract/mineral base oil mass): (i) an extract obtained by solvent refining of a deasphalted oil of a vacuum distillation residue, having a DMSO extractable content of less than 3 mass %; and (ii) a mineral base oil comprising a raffinate obtained by solvent refining of a vacuum distillate, or a mineral base oil obtained by hydrorefining and/or dewaxing of a raffinate obtained by solvent refining of a vacuum distillate, those mineral base oils having a DMSO extractable content of less than 3 mass %, a kinematic viscosity of 4 to 20 mm 2 /s at 100° C., a % C A of 3 to 20, an aniline point of 120° C. or lower, and an aromatic hydrocarbon content of 10 mass % or higher as determined by chromatography; wherein the process oil has a kinematic viscosity of less than 32 mm 2 /s at 100° C., a % C A of 15 to 30, an aniline point of 100° C. or lower, an evaporation mass variation percentage of 0.5% or lower, and a mutagenicity index of less than 1.