The cylinder-piston group inspection is performed in various ways. Measurement of compression inside the cylinders is the most common method. In vehicles with a gasoline engine, you need to unscrew the spark plugs, fill 30-50 ml of oil into each hole and cover them with a dry cloth: it will absorb excess lubricant. Then you have to rotate the engine by 3-4 turns with a starter and measure the compression. If it has raised to 0.9-1.2 mPa, the piston rings are worn out. In diesel engines the lubricant is filled in the same amount, but you need to install the glow plugs back, and then try to start the engine. If at positive ambient temperature and with non-working plugs it has started, then the piston rings are most likely to require replacement.
A more comprehensive inspection can be done at a service station. Typically it is performed using compressed air or vacuum method, it is quite time consuming, but at the same time provides more reliable results.
You may identify that the piston rings need to be examined by the following symptoms:
