More observations about DOT3 and DOT4 brake fluid:

Both DOT3 and DOT4, over time, adsorb water from the atmosphere. As they do so,
their boiling point lowers. One more reason to change the brake fluid sooner
rather than too late.

DOT4 is more hygroscopic than DOT3 (adsorbs water more quickly) and would
therefore need to be changed more frequently than DOT3.

Larry who started this thread.