Brake Fluid. Shelf life?

I opened a bottle of Honda brake fluid in June. I closed the lid tightly and haven't opened the bottle since then.

Is this fluid still good to use? I've heard that it attracts moisture after the bottle has been opened.


Yes, glycol based brake fluid is hygroscopic, so it is designed to absorb some level (3% max?) of water. If the container has been sealed since the last use, it should be fine. However, if it is something that you will continue to wonder if it was ok to use, then just buy some new stuff. Sometimes, peace of mind is worth the $6 :thumbsup:

Are you in an area that's been humid during this period? This makes a difference. I've used previously opened brake fluid that spent years on the shelf in my garage in AZ w/o problems.

Sounds like good advice. And yes, I'm at the beach which is pretty humid.

If its in a plastic bottle toss it. Metal...its probably okay.

Brake fluid should be changed every year or two on a car depending on the manner of use. For a bike, really it should be done frequently (though I'm guilty of blowing it off).

Just on the shelf life issue, over to transmission oil for a moment if I may....

I use motul 10w40 2t gearbox oil in my sons '05 YZ 85, and a half full bottle that had sat for 6 months or so, untampered, sealed well, looked as if someone had poured half a cup of old diesel engine oil into it when I opened it to use it....

This blackish gunk substance had found its way to the bottom of the bottle.

Did it just need a good shake up or was I lucky I pour it in a beaker prior to pouring it into the bike ?

I disposed of it and purchased a new bottle to be safe.

My thanks in advance.

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