DOT 3, 4 5.1 application

[nthach]

AFAIK, DOT3 fluids absorb less water and can have a higher dry boiling point. The Japanese OEMs use a weird DOT3 fluid - it has borate esters like a European DOT4 and lubricants. DOT 4 came in Super variants(Pentosin Super, ATE Type 200) with higher boiling points and LV variants. DOT5.1 was more of an aftermarket thing but called for by Ford in cutaways and probably Ferrari as stock on streeted cars.

Toyota still calls for DOT3 on all but the BMW-built MKV Supra. Else, the Japanese all say DOT3/4 is OK. I have ATE SL6/Bosch ESI 6 in two Lexii, and Prestone Max DOT3 in a Prius and Prestone DOT4 in a Sienna. The Prius is a less demanding braking application but has a known issue with brake actuators, the Sienna won’t benefit from low-viscosity fluid, it’s ABS-only.

Honda says DOT3 fluid on their cars, but their bikes require DOT4.

 

[dubber09]

I personally went with Bosch ESI6-32N Brake Fluid on all BF changes and it works great, changing it every 3 years.

 

[bonjo]

Firstly, I came to the conclusion that the independent garage not willing to use dot 5.1 most probably assumed it was a derivative of DOT5 without looking into it (case of little knowledge is worse than no knowledge??. Not being able to talk to him/ her directly, I will never find out!

Moving on, I decided to give our toyota dealer for the service as well before making a booking. To my surprise, they cost was lower than the independent garage and use toyota branded fluid. So this is where I'll have the job done.

 

[denwood]

DOT 3 is NOT less moisture absorbent than DOT4, but DOT 4 does need to be changed more often.

Bendix provides an insight into the importance of Brake Fluid - Issue 12 | Bendix Brakes

www.bendix.com.au

"Often not mentioned is the effect of the different DOT 4 formulation on the brake fluid behaviour. DOT 4 absorbs moisture at a slower rate than DOT 3 but is more susceptible to suffering a drop in its boiling point.
Typically a DOT 4 brake fluid will suffer a boiling point drop of 50% once it takes in 2% moisture while a DOT 3 brake fluid would only lose 25% of its boiling point at 3% moisture contamination although it takes in moisture at a faster rate. This suggests that DOT 4 brake fluids offer more stability and safety for longer but would need to be replaced at the recommended OEM intervals before it suffers a substantial drop in boiling point."

Not correct..DOT 3 absorbs water slower than DOT 4, and DOT 4 slower than DOT 5.1.

Also, DOT 5.1 absorbs moisture faster than DOT 3, however retains a higher boiling point given the same moisture content.

Brake Fluid Military Testing - DOT 3 v DOT 4 vs DOT 5.1

I have been researching brake fluid for a bit now to determine if a switch from DOT 3 to DOT 5.1 makes any sense for our vehicles. The one I'm most concerned about is our 2018 LEAF EV which calls for yearly fluid flushes, and has a very expensive integrated electronic braking system. We also see...

bobistheoilguy.com

The military examination referenced above also included a lab test exposing DOT 3/4/5.1 to high moisture and then testing absorption...then correlated to boiling points.

If you want an excellent DOT 3 that has low viscosity, excellent low temp viscosity, and boiling points that rival or exceed many DOT 4 fluids, AC DELCO Brake and Clutch fluid is what you want. Again, see the referenced thread

I've switched all of our vehicles (including our EV) over to the Bosch 5.1 fluid. All are DOT 3 spec cars. So far so good.

 

[reddevil]

I have a nissan qashqai(rogue sport) 2015 and the brake fluid has never being replaced. The independent workshop that I take to keep saying they have tested the fluid and is ok and not to waste my money. I keep saying I wanted to replace the fluid on each annual service but they are reluctant to take my money and showed me the "pen" test reading. I noticed the brake fluid is on the "low" side but hard to see since the fluid is still clear and about the same color as the container. Didn't want to open it until the next service.
There is no issue with braking and had front brake/rotor replaced 2 years ago.
Should I get the fluid replaced (even if I have to take it to another workshop)?

 

[denwood]

Every 2-3 years should be just fine with DOT3. It's not just water that is the issue, it's also the corrosion package...that's why copper testing strips should be used also if you're relying on tests. Given time/cost of testing, it's not a big deal to flush fluid, particularly if the brake pads/caliper pins are being serviced yearly.

 

[930.engineering]

I have a nissan qashqai(rogue sport) 2015 and the brake fluid has never being replaced.
.......
Should I get the fluid replaced (even if I have to take it to another workshop)?

For sure. Every two years is what I do.
.

 

[bonjo]

interesting readdenwood.

Re fluid testing pens, I have been told they are very unreliable. Perhaps expensive professional ones are accurate.

 

[Yah-Tah-Hey]

Valvoline DOT 3/4 every two years using Russel Speed Bleeders. System stays clean and no rust found in calipers during 2021 rebuild.