Working fluid

A working fluid whose base material is constituted by triethylene glycol monomethyl ether and further comprising polyethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, and combinations thereof;

• and which contains a modified silicone oil having a polar group, wherein the polar group is constituted only by an amino group and a polyether group,
• wherein the modified silicone oil has a structure expressed by Formula (1):
• X:
• Polar group;
• R1, R2:
• Group selected from among an alkyl group or alkoxy group with 1 to 30 carbon atoms, polar group identical to X above, and alkyl group or alkoxy group with 1 to 30 carbon atoms and having the polar group denoted by X above;
• R3, R4:
• Methyl group or phenyl group;
• l, m, and n are all 1 or greater, and l+m+n is 2000 or less, and
• wherein the content of the modified silicone oil is 0.002 to 0.7 percent by weight,
• said working fluid containing one or more additives selected from among lubricant, wear-proof agent, viscosity adjustment agent, bactericide, rustproof agent, antioxidant, extreme-pressure agent, pH adjustment agent, dye, and defoaming agent.