The research focuses on finding planning methods based on measuring and monitoring the basic indicators of internal combustion engines (Diesel engines) in order to determine the critical case of the engines, which determines the expected time for the engine or for some of its basic parts to be sent for comprehensive maintenance. The wear ratio of one of the basic components of the engine was also determined, we also chose the diameter of the cylinder and the corrosion that happens to it in order to determine the engine's lifetime and determine the moment when the engine should be sent for comprehensive maintenance. By observing a large number of engines put in repair in the industrial area in Lattakia, which are 30 engines of different types of diesel and gasoline, and with different capacities, it was noticed that about 15% of these engines were not exploited and invested the entire work period designed for them. Also it was noticed that 20% of them have stopped working because of the severe corrosion of parts, components and mechanics of these engines, which led to their damage and their inability to do their work on a regular basis. This has contributed to increased consumption of fuel and Lubricating materials, which causes damage to the national economy. The proposed planning method for determining the critical case of the engine when comparing the schematic results with the practical results of the engines has proved its efficiency and accuracy with an error rate of no more than 6% This allows it to be applied and adopted as an effective way to determine the actual lifetime of the engine and compare it with the life time of investing the engine mentioned in the manufacturer's catalogs when operating the engine under normal conditions.