When to replace brake fluid
 

After quite a bit of research, I cannot find when the actual time to change brake fluid. Everyone just says, "after 2 track days" or "every six months" or something like that. Is there a test or an analysis you can do to determine that it needs to be changed?

Thanks in advance

Whenever the brake pedal gets squishy.

"brake fluid test strips"

A bleed and topping off of fluid every 1-2x track days is cheap insurance, the strips to confirm that at least what's in the reservoir hasn't broken down.

You can use a brake fluid moisture test kit. They come in strips or you can buy an electronic tester. It's sometimes hard to gauge how squishy your pedal can become over time... unless it's like right after a track day.

If you're not driving it too hard around every 30k is about right.

Take a look at it. It should be almost clear. If milky, rusty coloured, or blackish then it needs to be changed. It should smell sort of sweetish (hard to describe an odour) and if there is any hint of a burnt smell it should be changed and flushed.


Everybody drives differently so there is no hard and fast time limits or operating condition that says "change it now". Rules of thumb is the harder you drive the car the more often you need to check it.

If braking heatload has never been to squishy/fading brakes and to boiled fluid, imho it may last long enough, at least i'd change never boiled fluid at most once per year. But then again if track is mentioned .. it's easy to abuse brakes above their capacity :). BTW, if you boil them often enough, maybe worth considering instead of frequent flushes change fluid to one with higher boiling temps / enhance cooling (eg. airducts) / reduce braking heat load (eg. shorter sessions / pedal dance instead of with nannies / braking lessons by hpde instructors ) .. or move to BBK.

Squishy pedal? Change it. Fluid is not amber? Change it. 2 years old? Change it.

Or use Project Mu. Green turns clear if it absorbs too much moisture (aging), or turns brown if it gets too hot (tracking).

PM to order.

Don't forget to bleed your clutch pedal every 2 years too.

I switched to Motul at 30k, made a huge difference. It was easy to do and not all that expensive.

I track it about once every other month. I have heard about the moisture test strips but is there any other way to test it for being broken down? I'm not really even sure if brake fluid breaks down from heat cycling. I have three track sessions on my current brake fluid and bled them about 6 months ago. I have not noticed any decrease in pedal feel. I'm using Motul RBF600.

Test strips are the objective test. Pedal feel is the subjective test. There is no other way to test, unless your fluid has a provision to indicate moisture.

So moisture is the only thing harmful to brake fluid? It can't break down due to heat?

Fluid degredation from heat is an indicator that the *real* solution to your problem is to increase capacity with a well designed BBK.

Band-aid fixes include higher grade brake fluid.

So either that or flushing brake fluid more often. I don't think a BBK is necessary for this lightweight car. I have no problem flushing brake fluid, I'm just trying to figure out how to determine that the fluid has degraded from heat.

How many pads do you have to burn up and how many times do you have to flush fluid, before you've covered the cost of a BBK and then some?

Why does Subaru now provide a factory Brembo setup if it's unnecessary?