Water is not more dense than brake fluid!! (type 3 and 4) Look up the specs on brake fluid, it clearly has a higher density than water, the specific gravity of brake fluid is about 1.05. Water is 1.0 by definition. There is no debate on this, the spec sheet from all brake fluids has this data. It is irrelevant anyway, because water and brake fluid are compatible and so will mix to form a uniform solution.