Provided is hexaester of bispentaerythritol monoformal, which comprises the bispentaerythritol monoformal represented by the following formula (I), and any one of carboxylic acids selected from C8 and C9 branched aliphatic monocarboxylic acids:
The hexaester has well-balanced excellent characteristics, such as low temperature properties and oxidation stability, and is used for industrial lubricating oil, such as a refrigerant oil composition.