Shelf life of DOT4 in opened container?

[markw996]

I'm reading conflicting information about brake fluid absorbing water.
In real world situations is brake fluid that's been open for 4 months (stored in the garage with lid tightly fitted) ok to use?

I ask because if brake fluid absorbs water at such an alarming rate, surely it's not that much better in the car reservoir....

BTW the fluid I've just changed has been in my bike for 10+ years so the 4 month old fluid must be an improvement, right?

[HustleRussell]

I'd use it

In fact the fluid I put in my BMW was opened a couple of years ago. Yes, the fluid is hydroscopic but in an unventilated container at garage temperature with zero agitation the rate of contamination is going to be much lower than it is in use.

To be honest 2 years is a bit extreme but as you say it'd have been better than what was in there and I'm going to change it again in two years so I'm not worried.

[PaulKemp]

A bottle of fluid is less than a tenner
If your just topping up probably OK but if your bleeding the brakes and putting a good volume through it then a Saftey issue and I always use new

[IainXE]

I would happily use it after 4 months.

[George111]

markw996 said:

I ask because if brake fluid absorbs water at such an alarming rate, surely it's not that much better in the car reservoir....

That's why it needs to be changed every couple or three years.

markw996 said:

BTW the fluid I've just changed has been in my bike for 10+ years so the 4 month old fluid must be an improvement, right?

After 10 years a lot of the moisture will be in the callipers which will help them to corrode. If you're changing the fluid after 10 years I'd pop the callipers off and have a look inside and give them a good clean.