Most of us don't pay allot of attention to our brake fluids but we should.
Did you know that water gets absorbed in the fluids even the stuff on your shelf.
The new DOT 5.1 has half the boiling point of the DOT 4.
Doing my brakes and wondered if my brake fluid new on the shelf was still good and I read ...NO.
I read after two years you should change it.

 

How would water get into brake fluid on the shelf?

 

Temp swing condensations, ambient moisture, the stuff is somewhat hygroscopic.

 

yes, fresh sealed fluid would be best. sealed fluid from your shelf should be okay. open bottle with a closed cap, no.

i'm an idiot though

 

Brake fluid draws in moisture from the air. Brake fluid is cheap. i have speed bleeders on my bikes and I flush the brake fluid every two years. It's inexpensive, easy to do, and doesn't take much time at all to do.

 

Fluid in your system goes bad over time but it would take decades to go bad in a closed container, even if it was opened and the cap was put back on.

 

Cheap insurance and it is simple to do; I flush the fluid every spring. I buy a small bottle and use it all flushing the brakes. I never save an open bottle. Overkill? Yep. But I do like being able to stop this beastie

 

Curious if anybody here has ever boiled the fluid in their lines/pistons and had a lever collapse from it...

 

https://en.wikipedia.org/wiki/Hygroscopy

 

Never heard of it. But maybe if you were pulling a trailer off the top of Pike's peak and rode the brakes all the way to the bottom.