This subject has been discussed before, on the IML W/some controversy as to the benefits of silicon brake fluid. I can only relate my experience with it's use. I have used DOT 5 silicon in my 39 Imperial C24 & 1937 Airflow (Since sold). Previously I would have to go through my Airflow brakes (W/ DOT 3 fluid) every spring after having it sit outside during the winter. DOT 5 silicon solved that problem. You are correct in noting, the DOT 3 will attract water. It will also react to the Dot 5 fluid. The secret for switching to DOT 5, is to clear the lines of Dot 3 before adding DOT 5. I used alcohol & air pressure. ALL rubber parts, hoses, cups etc. must also be replaced as the DOT 3 has leached into the rubber components. I had karps@xxxxxxxxxxxx in southern California resleeve my wheel cylinders. Jim Martin ........ Sunnyvale, Calif. http://www.imperialclub.com/yr/1939/limo/martin/index.htm