Does this brake fluid really need to be changed? (see photo)

[texases]

I guess my question is why did they EVER settle on these brake fluids, and not go with petroleum based hydraulic fluids?

[Renegade]

@texases

I guess my question is why did they EVER settle on these brake fluids, and not go with petroleum based hydraulic fluids?

I hope someone has the answer for this as I am also curious as well.

[Tester]

Brake fluid has to be able to cover a lot of criteria that hydraulic fluids don’t. Firstly think of a car on a mountainous road doing a lot of braking to the point where the cars discs are themselves glowing red. The brake fluid itself is therefore operating at extremely high temperature and yet every time you brake you expect, near enough, the same braking efficiency. And yet even after this journey you would use the car on numerous occasions and probably never even think of what is happening to the brake fluid itself. This scenario is well covered by using a proper brake fluid that has been designed to do that kind of job.
If it were ordinary hydraulic fluid in the system, certainly a mineral oil, the oil would absorb oxygen bubbles, even water, and with continual boiling the additive package would rapidly break down and think of what kind of braking you would have then with a very soft spongy brake pedal with a dramatically reduced braking efficiency.
Oils are designed to do a particular job and manufacturers spend enormous sums of money to get the best results for specific jobs.
If the manufacturer states a DOT4 fluid as brake fluid, that’s what should be used.

Tester

[pyrolord314]

@NYBo

A guess: DOT 5 costs a lot more than DOT 3. Combine that with the need to change out some brake components, the benefits to the average owner of the average vehicle doesn’t outweigh the costs involved. Remember, the manufacturers have set brake fluid change requirements that prevent the vast majority of water contamination problems anyway.

I was looking on Wikipedia, apparently DOT 5 also is incompatible with ABS systems, which last time I checked was required from 2012 on, so that’s probably the biggest reason.

[texases]

Absolutely use only the type of fluid specified for the car, of course!

I hadn’t thought about heat, but engine oil deals with heat, and hydraulic fluid is mostly oil…

[oilman]

I’ve just changed mine in my 2015 rav at 71K. the first change was at 48K (2 years ago). I had two 1994 camrys and a 2005 camry that went just over 200K before trading in or giving 1 away (the 2005 camry only went 186K due to front end damage) and I never changed their brake fluid ever. But from all research, they recommend between 2 and 4 years for a change. it’s easy and you can do it yourself.

[oilman]

or if you know a chemist in a lab, they can run a KF (karl fisher) water test on it.