Originally Posted by ST2008
Originally Posted by slacktide_bitog
As already said, all DOT 3 and DOT 4 are compatible with no problem. One quart is usually enough to bleed the whole system. And speed bleeders are awesome
I'm not sure one quart is enough. The rupture of the brake line was so significant that the master cylinder was emptied.
Besides of all DOT3 brake fluids need to met DOT specifications, do they have different qualites like engine oil (synthetic, anti-corrosion, anti-moisture etc)?.
Just as a point of clarification, if you see the work "synthetic" on a bottle/can of brake fluid, ignore it. All brake fluid is synthetic by definition. They're all made by a chemical and not a refining process. But by the same standard soap is "synthetic" since it's a chemical process of synthesizing soap from a fat. So is shampoo since detergents are synthetic chemicals.
The standards are published by the US government as part of Federal Motor Vehicle Safety Standard 116 (49 Code of Federal Regulations 571.116).
https://www.govinfo.gov/content/pkg/CFR-2011-title49-vol6/pdf/CFR-2011-title49-vol6-sec571-116.pdf
They set the minimum dry and wet boiling points for DOT 3/4/5. DOT 5.1 is barely mentioned, but it's assumed that it has to meet all the performance requirements of DOT 5. By definition DOT 5 is silicone while DOT 5.1 is glycol that's inherently compatible with DOT 4 and DOT 3 fluids. If you're worried about there being some incompatibility because a little bit of the previous fluid is in there, don't worry about it. I remember once I provided a bottle of DOT 4 brake fluid for a shop to use, and when it wasn't enough they supplemented it with a bottle of a different brand of DOT 4. They said it's not really a problem since they'll mix just fine and the additive chemistries are pretty similar. The required viscosity of DOT 4 is lower than DOT 3. DOT 5's required viscosity is even lower. I believe a lot of the testing requirements are the same for all grades of brake fluid, although there are some tests (like the pH test) that can't
The other important thing is the color. Silicon brake fluid must be dyed purple. DOT 3/4/5.1 must be clear to amber. There was a non-compliant DOT 4 brake fluid that was blue (ATE Super Blue). Apparently some would alternate using that with an amber brake fluid to help with flushing. If it had blue brake fluid in there, it would be bled until it started coming out amber. If it had amber brake fluid it would be bled until it started coming out about the shade of blue as the blue brake fluid. You can't get that in the US any more because it doesn't meet the FMVSS 116 standard. Not sure about Canada though.