Refrigerator oil, and working fluid composition for refrigerator

A refrigerating machine oil, comprising:

• a low-viscosity hydrocarbon oil having a kinematic viscosity at 40° C. of 6 mm2/s or lower;
• and
• a high-viscosity hydrocarbon oil having a kinematic viscosity at 40° C. of higher than 400 mm2/s;
• wherein the high-viscosity hydrocarbon oil is a residual oil hydrocarbon base material selected from the group consisting of
• an atmospheric distillation residual oil of a crude oil,
• a vacuum distillation residual oil of the atmospheric distillation residual oil,
• a deasphalted oil of the atmospheric distillation residual oil or the vacuum distillation residual oil,
• a solvent extracted extract oil of the deasphalted oil,
• a solvent extracted raffinate oil of the deasphalted oil, and
• a refined oil of the atmospheric distillation residual oil, the vacuum distillation residual oil, the deasphalted oil, the solvent extracted extract oil or the solvent extracted raffinate oil,
• wherein the refrigerating machine oil has a flash point of 130° C. or lower and a carbon residue of 10% residual oil of 0.02% by mass or more, wherein the carbon residue of 10% residual oil is measured by the Micro method in accordance with JIS K2270-2:2009 for residual oil obtained by distilling the refrigerating machine oil and removing distillate oil having a volume fraction of up to 90%, and wherein the refrigerating machine oil is used with a refrigerant.