One more point that comes to my mind. As I remember the holding capacity of coolant including distilled water is 3.6 litres( ? ) for M- 800. If so, we normally add distilled water in the Ratio of 2:1, means 1.2 litres of coolant and 2.4 litres of distilled water, right? so in the 2nd and 3rd flush we need 3.6 + 3.6 litres = 7.2 litres distilled water. Later we fill up 1.2 litres of Coolant and 2.4 litres of distilled water. So 10 litres of distilled water is sufficient for Radiator flushing work.