A method of operating a compression ignition internal combustion engine wherein (i) the engine includes a reciprocating piston operable within a cylinder for placing a combustible fuel/air charge under compression within a combustion chamber sufficient to cause self-ignition when operating at a predetermined elevated engine temperature; and (ii) a glow plug having a heating element projecting within the combustion chamber to provide sufficient heat to the compressed fuel/air charge to ignite it when starting or operating the engine below said predetermined elevated engine temperature. The method comprises (a) providing power to said glow plug and initially establishing the temperature of the heating element at a temperature exceeding 1600.degree. F.; (b) starting the engine; (c) concurrently continuing to operate the engine and maintaining the heating element temperature at least at 1600.degree. F. until the engine temperature is sufficient to cause self ignition of the compressed fuel/air charge without the additional heat energy provided by the heating element; and (d) maintaining the heating element at a temperature exceeding 1600.degree. F. throughout at least a portion of the entire remaining period of operation of the engine (and preferably between 1600.degree.-2000.degree. F. during the entire period of operation).The method also includes the option of reducing the power supplied to glow plug in fixed decrements and continuing power to the glow plug at the decremented voltage level for as long as the current plug voltage is available at the decremented voltage level.