Depends on whether it's very hygroscopic or not, and how well sealed it is - I prefer to use small bottles, and dump any opened ones rather than keep them. It's amazing how they can absorb water from what is seemingly a well-sealed bottle (the reason they always have that foil seal on top when new!)
It's also why I NEVER recommend the often touted "trick" of tying the brake lever open with reservoir cap off and leaving the system open all night to purge the bubbles in the lines - you may end up with 5% water overnight in high humidity conditions - perfect opportunity for a case of brake-lock when the water turns to steam in hard use....
I'm not a scientist or anything, but I would imagine the shelf life of an opened bottle of anything hydroscopic is reduced greatly in high humidity areas. I'm sure its worse for Norm and I here in NC with all of the humidity, even with super-tight lids. Not sure about the humidity in AZ. I also pitch the bottle within a day of opening it. When I bleed I like to get the old fluid out anyways, so I usually run a good amount through the lines.
perhaps its just me... but brake fluid can easily be had on the cheap...
why not just buy new when you need it... sometimes "Better safe than
sorry" is a good motto - specially when you are putting a 4 buck item
in a 10-20k bike.
The screw on the cap of a bottle is just as good I would think as the cap on your brake resorvoir right? Therefore if they recommend you change your brake fluid every 2 years (ducati says this) on your bike then I would think that stuff sitting on the shelf for a few months is fine. But I wouldn't think you want to leave it sitting there for 2 years.
Although brake fluid may be cheap, to just throw it away because it's been open once is wasteful. Unless you're a MotoGP racer I don't think you'll notice a difference in brake fluid that's been on the shelf for a month.
Agreed, I put a double layer of clear plastic wrap over the top and screwed the cap on tight. I figure this is as good or better than the original seal. I'm not a cheapskate but I figure why waste? And where is that extra fluid disposed of? Not down a drain or in your back yard I hope.
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