On motorcycles the standard manufacturer’s maintenance schedule calls for brake fluid flush every 2 years. Automobile manufacturers tend to never specify brake fluid replacement, for some unknown reason. I have found new brake fluid at 4 years makes a big difference in braking feel.
As for rust, I think thats the least of one’s worries about water in brake fluid. Water lowers the boiling point of brake fluid. Boiling brake fluid means no brakes.
DOT 4 brake fluid boils at higher temperatures than DOT 3. And DOT 5.1 boils at even higher temperatures.
$200 is outrageous. $6 of brake fluid (a quart), 24" of vinyl hose, a glass jar, a wrench, and a helper for 30 minutes is all it takes to change.
I recommend keeping a quart of isopropyl alcohol handy with the cap loose when dealing with brake fluid. A little on your fingers will etch fingerprints in pretty paint.
BMW has been specifying brake fluid replacement every 2yrs for 25yrsor more. BMW leads the way in new technology and has well thought out service requirements
“Automobile manufacturers tend to never specify brake fluid replacement, for some unknown reason”
That may apply to US auto manufacturers, but that does not necessarily apply to all auto manufacturers.
For instance, Subaru specifies a brake fluid change ever 36k/3 yrs.–a schedule to which I adhere faithfully. I believe that most, if not all, of the Japanese auto manufacturers have similar maintenance requirements.
Mine has a time listed for it (VW 2002 NB). I believe it is 2 years, and I make sure it is done.
I will suggest that anyone having ABS or stability control, not be too fast to do it yourself. Make sure that you really understand the procedure for YOUR car, which may be different that your neighbors and certainly different than your father’s car.