Abstract: The service life of conventional glow plugs is extremely short when they are continuously energized at an elevated temperature during engine operation in order to assist ignition of non-autoignitable fuels. Such glow plugs typically fail due to thermal stresses and/or oxidation and corrosion.Herein is disclosed an improved heating element assembly adapted for incorporation in a glow plug. The heating element assembly includes a monolithic sheath having a relatively-thin and generally annular wall defining a blind bore. The heating element assembly further includes a heating device positioned in the blind bore and adapted to emit heat, and a heat transfer device adapted to transfer heat from the heating means to the sheath. The heating device includes a heating filament and a ceramic insulator. THe heating filament is protected against oxidation by being encapsulated in the insulator. The insulator is protected against corrosion by being encapsulated in the sheath.