FIELD: engine making, improvement of lubrication conditions and optimization of design parameters of parts of cylinder and piston group of internal combustion engine. SUBSTANCE: moment of separation of oil layer at level of microirregularities is measured in agreement with proposed method, condition of semi-fluid friction is evaluated as well as stable uninterrupted contact with registration of its duration by angle of turn of engine crankshaft. EFFECT: invention makes it possible to approximate geometrical characteristics of engine, in particular, diametrical clearances between piston and cylinder to optimal ones.
