摘要 |
The invention provides a lube oil which exhibits low vapor pressure despite having low viscosity, is non-flammable, exhibits excellent heat resistance, has tribological characteristics equivalent to those of conventional hydrocarbon-based lube oils, and can be used for a long time under very severe conditions such as high temperature and vacuum. The lube oil contains, as a base oil, an ionic liquid formed of a cation and an anion and having an ion concentration of 1 mol/dm<SUP>3 </SUP>or more.
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