Cylinder lubricating oil for a low-speed main propulsion diesel engine is admitted to each cylinder during which stroke?

      Cylinder lubricating oil for a low-speed main propulsion diesel engine is admitted to each cylinder during During the compression stroke.

                 Cylinder lubricating oil, for lubricating the piston rings and the liner, has to be admitted when the piston, piston rings and the liner are in cool condition and the piston is moving upward so that oil can be retained on the piston rings and sprayed by the piston rings on the liner walls. This is only possible during the compression stroke. Otherwise, the piston is hot and if the lubricating oil is sprayed on it, it will evaporate very fast and will not carry out any work of lubrication. At the same time, if lubricating oil is injected during the expansion stroke, i.e. when the piston is moving downwards, it will have a scrapping effect rather than lubrication.