The flushing oil is used to clean lubrication systems of internal-combusting engines without their disassembly. The formula is developed based on hydrocracked base oils made with a high purification degree. A special selected additive package comprises the efficient combination of detergent, dispersive and anti-wear ingredients. The oil dissolves accumulated deposits in the oil system channels and in the internal engine cavities within a short period (from 10 to 20 minutes of warmed-up engine operation). It helps fully remove hard particles of motor oil degradation, unburned fuel (ash) and wear particles of the engine loaded parts from the engine.