dot 5 vs dot 5.1

[jims94vmx]

Is it a bad idea to use dot 5? I had dot 5.1 in the system already and
while running around stopped at an autozone and all they had was the 5.0
Using for clutch if that matters?

Thanks.....Jim

 

[Traumahawk]

DOT 5 is a silicone based fluid, 5.1 isn't. I've always been told that they don't mix very well.

 

[one2dmax]

Do NOT mix. You can get dot 3 or 4 and mix ok.

 

[VMAX1260]

DOT 5 is one of several North American designations of automotive hydraulic brake fluid, denoting a particular mixture of chemicals imparting specified ranges of boiling point.
DOT 5 is a silicone-based brake fluid (contains at least 70% by weight of a diorgano polysiloxanehttp://en.wikipedia.org/wiki/DOT_5#cite_note-1
Unlike polyethylene glycol based fluids, it is hydrophobic. An advantage over other forms of brake fluid is that silicone has a more stable viscosity index over a wider temperature range. Another property is that it does not damage paint

Using DOT 5 in a DOT 3 or DOT 4 system without proper flushing will cause damage to the seals and cause brake failurehttp://en.wikipedia.org/wiki/Wikipedia:Citation_needed. DOT 5 brake fluid is not compatible with anti-lock brake systems. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.

DOT 5.1 is one of several designations of automotive brake fluid, denoting a particular mixture of chemicals imparting specified ranges of boiling point.
A brake fluid's dry boiling point is the temperature at which the pure fluid will boil. Wet boiling point concerns the boiling temperature when the fluid contains water.
In the United States, all brake fluids must meet Standard No. 116; Motor vehicle brake fluids.http://en.wikipedia.org/wiki/DOT_5.1#cite_note-1 Under this standard there are three Department of Transportation (DOT) minimal specifications for brake fluid. They are DOT 3, DOT 4 and DOT 5.1.
DOT 5.1, like DOT 3 and DOT 4, is a polyethylene glycol-based fluid (contrasted with DOT 5 which is silicone-based). Polyethylene glycol fluids are hygroscopic and will absorb water from the atmosphere, which is necessary to prevent sheer and undiluted water in the braking system, which is very corrosive, also water droplets can freeze in the pipes, thus blocking the system.
DOT 5.1 is the non-silicone version of DOT 5, defined by FMVSS 116 as being less than 70% silicone. Above that threshold makes it DOT 5.

 

[RaWarrior]

As said, don't mix. Use the same spec fluid, or if you change, make sure to completely flush/bleed the lines of all the old fluid.

Dot 3/4 can be mixed, the only real difference is that dot 4 has a higher boil point.

 

[jims94vmx]

Thanks, I did a test in my measuring cup using dot 5.1 at the bottom then poured the 5.0 on top....the 5.1 is heavier and even when mixing it together will separate and again the 5.0 will go to the top. Never be in a hurry when doing these things! LOL

 

[one2dmax]

The problem isn't just the mixing. Even a good flush doesn't always get the old fluid/chemical out of the rubber and your seals will pretty much immediately go to shit.

 

[thor_eyerdhal]

Never use dot 5 in a non specific brake circuit even flushed. brake felling will be bad, like if there was air bubbles in it. Dot 5 is for military vehicules stored for months or years, not for daily driven ones.

You can mix 5.1 with 4 o 3 but it is always better when not mixed...

 

[davesax36]

I'm pretty sure any 5 mixed with 4/3= jello.

Sent from my Galaxy Nexus using Tapatalk 4

 

[one2dmax]

5.1 can be mixed. 5 (without the .1) can not be mixed.