Grease composition for a constant-velocity joint

A grease composition for a constant-velocity joint, the grease composition comprising:

• a mineral oil,
• a thickener,
• a molybdenum dithiocarbamate,
• a potassium borate hydrate, and
• a zinc dialkyldithiophosphate,
• wherein
• a content of the molybdenum dithiocarbamate based on a total amount of the grease composition is 1.2% by mass or more and 8% by mass or less,
• a content of the zinc dialkyldithiophosphate based on the total amount of the grease composition is 0.3% by mass or more and 2.0% by mass or less, and
• a content of the potassium borate hydrate based on the total amount of the grease composition is 0.28% by mass or more and 1.9% by mass or less, and wherein
• a mass ratio of the content of the molybdenum dithiocarbamate to the content of the potassium borate hydrate (molybdenum dithiocarbamate/potassium borate hydrate) is 2 or more and 13 or less,
• a mass ratio of the content of the zinc dialkyldithiophosphate to the content of the potassium borate hydrate (zinc dialkyldithiophosphate/potassium borate hydrate) is 0.5 or more and 3.6 or less,
• a mass ratio of the content of the molybdenum dithiocarbamate to the content of the zinc dialkyldithiophosphate (molybdenum dithiocarbamate/zinc dialkyldithiophosphate) is 3 or more, and
• the thickener is a urea-based thickener represented by a formula (2):
• in the formula (2), R4 represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, R5 represents a cyclohexyl group or a cyclohexyl derivative group having 7 to 12 carbon atoms, and R6 represents an alkyl group or alkenyl group having 8 to 20 carbon atoms.