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Brake fluid

T

T.O.Craig

Well Known Member
Howdy again,
I can't find anything in the instructions of what type brake fluid to use. I have dot 4 Motul high temp fluid that I use on motorcycles.What do you think?
 
Do not use automotive brake fluid - too corrosive. Use Mil-spec hydraulic fluid. I don't have the numbers handy but there is the 'standard' one, and the recommended one with a higher flash point.
 
Royco 782 is a good choice, I have a quart sitting in my garage which is probably about enough for two lifetimes. The more research you do the more options you'll find... some guys use ATF, I think. But MIL-PRF-5606H or MIL-PRF-83282 hydraulic fluids are the safe choices. Spruce has a good selection, as do other places.

The only universal no-no seems to be most automotive brake fluid.
 
Mobil 1 ATF (available anywhere)

I use this stuff. The specs on the container suggest it complies with MIL-PRF-83282...

http://www.qclubricants.com/royco/royco_782.htm

https://mobiloil.com/en/automatic-transmission-fluid/synthetic-atf

You can buy it locally (anywhere) with no hazmat charges. I really like this aspect.

I'm gonna GUESS Dot 5 brake fluid might work (silicon based - the seals will thank you). I have heard that high altitude exposure allows the air in the Dot 5 to expand...but I have not had that experience (I use it in my motorcycle clutch system; had it to 10500MSL with no issues).

Carry on!
Mark
 
I'm not sure about aircraft grade brake fluid but I know that Auto grade brake fluid is hydroscopic (absorbs water) so you can't keep open containers for use later. Water in the fluid will boil and cause braking problems. Others that are more knowledgeable in this area can comment.
 
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