Vacuum pump oil

A vacuum pump oil, comprising:

• a mineral oil (A) having a temperature gradient Δ|η*| of complex viscosity between two points of t(° C.) and t−10(° C.) (where −15≤t≤−10), as measured using a rotary rheometer at an angular velocity of 6.3 rad/s, of 10 Pa·s/° C. or less;
• and
• a phenol-based compound (B) and an amine-based compound (C),
• wherein the phenol-based compound (B) is a hindered, monocyclic phenol-based compound comprising an ester group, and
• the amine-based compound (C) is a diphenylamine compound,
• wherein the vacuum pump oil has a viscosity index of less than 160,
• the vacuum pump oil has an anti-emulsification degree of less than 20 minutes, as measured according to JIS K2520,
• the mineral oil (A) comprises a mineral oil (A1) classified into Group 3 of the API category and a mineral oil (A2) classified into Group 2 in the API category,
• wherein a content ratio of the mineral oil (A1) to the mineral oil (A2) [(A1)/(A2)] is, as a ratio by mass, 50/50 to 99/1,
• a content of the phenol-based compound (B) is in a range of from 0.02 to 2% by mass, based on a total amount of the vacuum pump oil, and
• a content of the amine-based compound (C) is in a range of from 0.02 to 2% by mass, based on the total amount of the vacuum pump oil.