The technique and features of micrometering of cylinder liners are presented. The main factors influencing the wear of the cylinder liner and the rules for assigning planes and sections when conducting a micrometer of its inner surface are theoretically substantiated. On the example of a study of used cylinder liners of engines of the Yaroslavl Motor Plant, it was revealed that the greatest wear is manifested in the place where the upper piston ring stops in the upper part of the liner, and the amount of wear will be greater in the swinging plane of the connecting rod due to the action of normal force during pressure distribution at the beginning of the expansion stroke. High wear at the top is also due to high temperatures and lack of lubrication. It was found that the diameter of the upper non-wearing band can be used to judge the initial size of the sleeve hole. The underside of the cylinder liner is subject to wear due to the friction of the piston skirt against its surface.