A fuel injector tip seal is provided including improved resistance to the heat and pressures of combustion gas. According to one aspect, the tip seal is formed from polytetrafluoroethylene and between 10 and 35 percent carbon fiber. The material offers improved surface finish and deformation resistance as well as improved thermal conduction and keeps thermal expansion low as compared to conventional fuel injector tip seal designs. According to a further aspect, a revised seal groove design is provided that allows for expansion and deformation of the tip seal and creates more pressure to the outside diameter face when pressure is applied at the tip. According to another aspect, the tip seal is formed of a flat disk-shaped seal body that can be assembled on the fuel injector by an assembly cone device that allows the disk-shaped seal body to be flipped to a ring-shaped configuration in its assembled position.