Not wasting brake fluid?

[YipMan_Style]

I did my brakes, use all that I needed. All done 4 weeks ago. There have been many writings and discussions about how once you open a bottle of brake fluid, it's pretty much going bad due to moisture absorption.

I have few onces left, because I bought the larger bottle. 5-6oz left. Do you think it's a good idea to just replace some of the "new" fluid currently in the reservoir? To just use it up?

Or best NOT to open the reservoir, so no moisture will be absorbed? And just dispose of new-unused brake fluid, properly of course?

 

[barryh]

I did my brakes, use all that I needed. All done 4 weeks ago. There have been many writings and discussions about how once you open a bottle of brake fluid, it's pretty much going bad due to moisture absorption.

I have few onces left, because I bought the larger bottle. 5-6oz left. Do you think it's a good idea to just replace some of the "new" fluid currently in the reservoir? To just use it up?

Or best NOT to open the reservoir, so no moisture will be absorbed? And just dispose of new-unused brake fluid, properly of course?

There would be no point replacing 4 week old fluid in the reservoir.

If the fluid in the reservoir was older then yes there is some benefit in exchanging just the fluid in the reservoir rather than throwing the fluid away as moisture will migrate to the new fluid, lowering the overall moisture content in the system.

I don't throw away a part used container of fluid. If it lasts 2 years in the reservoir then it will last at least two years in a tightly sealed container. I would still test it before use and have done so.

 

[D60]

I always say depends on humidity in your area. Very arid here so I have little concern about fluid in an opened container for 1-2 years. After that, it's inexpensive enough that I just dispose of it.

Walmart or RA (tacked on an order) have the best prices for big bottles of basic DOT3

 

[kschachn]

I did my brakes, use all that I needed. All done 4 weeks ago. There have been many writings and discussions about how once you open a bottle of brake fluid, it's pretty much going bad due to moisture absorption.

So since you’ve seen those, what was the conclusion?

 

[Donald]

Keep it for when you help a friend with brakes.

Keep a sealed container for your own brakes.

 

[John105]

I think you're fine to replace what's in the reservoir, with what's in the bottle. Nothing is harmed by opening the reservoir's cap.

But don't leave the bottle for too too long and use that next change. Luckily especially DOT 3 is what I consider cheap. And when I say too long, I probably do mean 2 years. In other words, I wouldn't use it for the next exchange or flush. I actually do not think 4 weeks is too soon because there have been many braking cycles over those 4 weeks. It won't help a lot but you can extract the amount of what you have left, and put it in as 100% clean.

On 2 of our cars I use a syringe to exchange at the reservoir. I got tired of bleeding at all 4. On my BMW, I bleed each caliper. So that's where my suggestion is coming from....