A grease includes a perfluoropolyether oil copolymer and a thickener mixed with the copolymer. The copolymer includes about 20 mol % to about 80 mol % of CF.sub.2CF.sub.2O units, about 20 mol % to about 80 mol % of CF(CF.sub.3)CF.sub.2O units, and about 0 mol % to about 45 mol % of one or more additional perfluoroalkyleneoxy units. The copolymer has a viscosity index in the range of about 120 to about 220. The copolymer has an average TFEO run length of less than about 6. A process of forming a grease includes mixing a perfluoropolyether oil copolymer with a thickener to form the grease.

A grease includes a perfluoropolyether oil copolymer and a thickener mixed with the copolymer. The copolymer includes about 20 mol % to about 80 mol % of CF.sub.2CF.sub.2O units, about 20 mol % to about 80 mol % of CF(CF.sub.3)CF.sub.2O units, and about 0 mol % to about 45 mol % of one or more additional perfluoroalkyleneoxy units. The copolymer has a viscosity index in the range of about 120 to about 220. The copolymer has an average TFEO run length of less than about 6. A process of forming a grease includes mixing a perfluoropolyether oil copolymer with a thickener to form the grease.

A heating device including: a rotating member for heating, an opposing member, which is arranged so as to be opposed to the rotating member, and forms a nip portion together with the rotating member, and a biasing member, which is arranged inside the rotating member, has an opposing surface with respect to an inner peripheral surface of the rotating member, and biases the rotating member to the opposing member. The inner peripheral surface and the opposing surface are brought into contact with each other via a grease composition to form a sliding portion. The grease composition contains a base oil. The base oil contains a fluoropolymer having a specific structure and a perfluoropolyether having a specific kinematic viscosity and a specific evaporation loss and having a specific structure.

A heating device including: a rotating member for heating, an opposing member, which is arranged so as to be opposed to the rotating member, and forms a nip portion together with the rotating member, and a biasing member, which is arranged inside the rotating member, has an opposing surface with respect to an inner peripheral surface of the rotating member, and biases the rotating member to the opposing member. The inner peripheral surface and the opposing surface are brought into contact with each other via a grease composition to form a sliding portion. The grease composition contains a base oil. The base oil contains a fluoropolymer having a specific structure and a perfluoropolyether having a specific kinematic viscosity and a specific evaporation loss and having a specific structure.