LUBRICATING OIL

摘要

Disclosed is a lubricating oil which has a low viscosity and a low vapor pressure at the same time, is free from a risk of inflammation and excellent in heat resistance. The lubricating oil has friction characteristics equivalent to those of the conventional hydrocarbon lubricating oils, and can be used for a long time under extremely severe conditions such as at high temperatures in vacuum condition. The lubricating oil contains, as a base oil, an ionic liquid which is composed of cations and anions and has an ion concentration of not less than 1 mol/dm<3>.