The Prius engine is not allowed to rinse with flushing oil. The liquid includes a very large quantity of kerosene and other corrosive solvents. In the case of washing, the thin oil valves of the valve and VVTi muff (modification of the gas distribution phase) may be clogged.
Also, rinse fluid cannot be completely washed out of the engine, and its residues can be blended with oil by changing its properties.
