LUBRICATING GREASE COMPOSITION

The invention provides a lubricating grease composition containing the following components (a) and (b): (a) an ionic liquid having as an anion bis(trifluoromethylsulfonyl)imide; and (b) as a thickener a diurea compound of formula (1): R1NH-CO-NH-R2-NH-CO-NH-R3 (1) wherein R2 is an aromatic hydrocarbon group having 6 to 15 carbon atoms; and R1 and R3, which may be the same or different are each an aromatic hydrocarbon group having 6 to 12 carbon atoms, an alicyclic hydrocarbon group having 6 to 12 carbon atoms or a straight-chain alkyl group having 8 to 20 carbon atoms, with the groups represented by R1 and R3 containing the aromatic hydrocarbon group in an amount of 50 to 100 mol%. The lubricating grease composition of the invention can favorably be used under ultra-high vacuum, and under high temperatures of 200 to 300°C.