Grease base oil and grease composition containing said grease base oil

A grease base oil, containing:

• condensation esters of alcohols (A) and carboxylic acids (B),
• wherein the alcohols (A) include a polyhydric alcohol represented by General Formula (1):
• wherein R1 to R4 independently represent a hydrogen atom, a methyl group, or a hydroxyl group, and at least two of R1 to R4 represent a hydroxyl group,
• the carboxylic acids (B) include a fatty acid having 5 or more and 9 or less carbon atoms (B-1), a branched fatty acid having 15 or more and 20 or less carbon atoms (B-2), a cycloalkane monocarboxylic acid having 4 or more and 8 or less carbon atoms (B-3), and an aromatic carboxylic acid (B-4), and
• the carboxylic acids (B) have a percentage of the fatty acid (B-1) of 30 mol % or more and 50 mol % or less, a percentage of the branched fatty acid (B-2) of 30 mol % or more and 50 mol % or less, a percentage of the cycloalkane monocarboxylic acid (B-3) of 10 mol % or more and 30 mol % or less, and a percentage of the aromatic carboxylic acid (B-4) of 1 mol % or more and 15 mol % or less.