Brake fluid recommendation needed

[hid3]

Greetings everyone.

I've got a Soviet era car ZAZ 968. Originally by specification it calls "БСК" fluid (which I believe none of you have heard of). It's 50:50 mix of castor oil with butanol. I believe this is comparable to DOT-2 brake fluid spec.
Some later years models came out of factory filled with "НЕВА" or "ТОМЬ" fluids, which, I also suspect you have no clue of...

The big question: since those mentioned ones are no longer available, what fluid should I use in this brake and clucth system? What I know for sure is that DOT-4 swells rubber parts for sure.
Is DOT-3 a bit more rubber-friendly than DOT-4? Any other options?

Thanks

 

[JavierH19]

It seems to be a really thin oil that is around 15-20 cst at 40c temperature so it's a bit thinner than 0w-8 at 40c and there is also mineral bike oil meant for bycicles. But you do not intend to use the car in cold temperature so I wouldn't be surprised if 0w-8/12/16 or a ultra low viscosity automatic trans oil or a really thin hydraulic oil will work just fine, perhaps a bit more tight to press. There's no seal compatibility issue with any of them since they're all petroleum oils unlike everything after dot 2. But what country are you in since selection differs a lot.

An example of mineral bike oil.
https://maximausa.com/products/mine..._content=sag_organic&utm_campaign=sag_organic

ISO vg15 oil is also very similar but is likely hard to get.

 

[slacktide_bitog]

Just mix the castor oil and alcohol yourself. I don't think DOT2 exists anymore

 

[hid3]

But what country are you in since selection differs a lot.

I'm in Lithuania

Just mix the castor oil and alcohol yourself. I don't think DOT2 exists anymore

Nope, DOT2 doesn't.
Folks have tried to mix castor oil + butanol. However, sediments fall out of suspension within weeks to months time... Or it would be more correct to say that phase separation happens

 

[Boomer]

What about a thin silicone fluid. This should not go after any rubber parts or seals and will bne a pure substance with no separation issues.

 

[hid3]

Isn't DOT5.1 silicone based? Is it an option to use straight DOT5.1 then?

 

[shortyb]

Isn't DOT5.1 silicone based? Is it an option to use straight DOT5.1 then?

I think 5.1 is still typical glycol based as it is compatible with DOT 3 & 4. DOT 5 is the silicone fluid and should be rubber component friendly. Only caveat I can think of with DOT 5 is the old fluid needs to be COMPLETELY flushed from the system or it does some evil Dexcool type gelling or such.