Posted by D Sherman [72.47.9.228] on Friday, September 09, 2011 at 20:53:52 :
In Reply to: Habit? posted by ChrisCase [67.121.210.113] on Friday, September 09, 2011 at 20:27:27 :
My main reason not to change is that I like to be able to flush the system out really well and DOT 3 is about $3/quart versus $15 or so for DOT 5. Also, it's nice to be able to just use a hose to rinse off anything that gets brake fluid spilled on, including myself. I keep the DOT5 in my M35s and M54 because they came that way from the DRMO and I have a couple gallons of army surplus DOT 5, but I can't see "upgrading" an old truck when the old DOT 3 is plenty good enough. It's like running ethyl in an engine made for regular. High temperature resistance is great, but on an old truck it's a solution to a problem we don't have. Water absorption and rust are always an issue in a brake system, but which is worse -- a lot of rust concentrated in one place, or a little rust everywhere? They both seem about equally bad to me.
The DOT 5 was surely designed to be compatible with all the same rubber materials used in brake hoses and cups so that retrofitting would be possible without a complete replacement of the whole system, so unless someone gives me evidence to the contrary, I'll believe that a slight film of old DOT 3 in a DOT 5 system is harmless.
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