A sequential injection lubrication system for a spherical rotary valve internal combustion engine operating on natural gas or alternative fuels, the lubrication system having a plurality of injectors, one for each cylinder, the injectors and communication with a lubricant reservoir and with a control unit which sequentially opens and closes the injectors for the introduction of lubricant into the cylinder, the control unit in communication with a control panel allowing the selective setting of the duration of the pulse injection and the frequency thereof.