Dot-4 Synthetic brake fluid, advantages?

Can it be used in a system that had contained regular Dot-3 if all of the fluid has been purged through all of the wheel cylinders?

What about Dot-5.1 non silicone brake fluid?

Jim

 

Jim, AFAIK the only real difference is the heat they are able to withstand before boil-off. I don't think there would be a problem, but no real advantage either. By the time boil-off occurs, your going to have brake fade in a big way so the boil-off point will be the least of your worries.

 

Thank KD93 i was wondering the same thing! i had got some when i was on leave and just put it behind the seat for a bad day. thanks for the info!

 

I read somewhere that the DOT-4 did not compress the same as DOT-3 and yielded much stiffer pedal response with less braking response.

I am not claiming this to be so, just that I did read it somewhere.

Also, in a similar discussion on a separate forum, silicone brake-fluids were not very highly recommended at all.

I can't recall the reasons, just that the silicones were not a good idea in a highway vehicle.

 

To my knowledge DOT4 is a higher boiling point (BP) glycol BF, but similar to the conventional DOT3. The silicon brake fluid (SBF) has the highest BP of all, but more importantly for my purposes is it does not take on water so does not promote corrosion as the glycol fluids do. I first acquired some SBF over 35 years ago, and have used it non-stop since in all brake fluid applications; top-up, component replacement fills and complete pump-thru fluid replacement. SBF is lighter than glycol fluid, and does not mix with it, so as a top-up it acts as a moisture barrier at the fluid-air interface in the reservoir. Obviously I'm a big fan of SBF and am prepared to address all the usual issues raised against it. Bring 'em on, ...

 

DOT5/silicone based fluids aerate VERY easily, AND the air stays entrained in the fluid, that`s why it is not recommended for anything with ABS as the pulsations of the valves can foam the fluid. It is notoriously difficult to bleed due to this About the only "benefits" are the fact that it is safe for painted surfaces and it is`nt hydroscopic but that causes its own issues regarding corrosion.

 

I found some information on it after I thought about it last night,

http://www.synlube.com/brake.htm

http://en.wikipedia.org/wiki/Brake_fluid

I did not know there was such a short service life on brake fluid.

Jim

 

I re-read Jim's original question and see that he asks about SYNTHETIC and NOT SILICONE.

I just assumed he was meaning silicone; but, after about three minutes of reading, I see that --- to my understanding --- synthetic is NOT particularly silicone.

I have never before heard of synthetic; and, if I have, I must have been seeing "synthetic" but reading "silicone".


I know absolutely nothing about the synthetic brake-fluids, so this is new knowledge to me.


Carry on.

 

I've been told 3 and 4 can be mixed. So I would think you could fill the master with 4 and bleed the system. It is also to my understanding that 5 CANNOT be mixed with anything! And furthermore 5 has a shorter service life. But I don't understand much so some further resource maybe needed.

 

Like Bearkiller, I too misread the original post. As ChrisLib says, synthetic is absolutely NOT recommended for ABS systems. Dot's 3, 4 and 5.1 are good for ABS, with increasing boil off points for each number. I can't remember what the boil off point for 5, (i.e. synthetic) is.

 

Ok now I am getting confused..

Are the words Synthetic and Silicone maybe getting confused with each other?

The Prestone website claims synthetic can be used on ABS systems?
Even the DOT-3 synthetic is recommended?

http://www.prestone.com/products/car...s/product_list

As does the Valvoline website.

http://www.valvoline.com/pdf/Valvoli...rake_Fluid.pdf

This is why I like air brakes, they just use plain air, nothing special.

Jim

 

Pulled from WIKI:

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.

As of 2006[update], most cars produced in the U.S. use DOT 4 brake fluid.

Using DOT 5 in a DOT 3 or DOT 4 system without proper flushing will cause damage to the seals and cause brake failure. DOT 5 brake fluid is not compatible with anti-lock brake systems

 

Same here, ... I missed the "synthetic" part and raced off on my SBF rant. I checked my Prestone SBF container: it makes no mention of ABS brakes but does say not to mix with DOT4 or DOT4 fluids. I have mixed SBF into my brake systems in every ratio necessary for several decades with only good results, but I wouldn't recommend it for others either. The 2yr change interval on DOT3 fluids makes it desirable for me to switch my vehicles to SBF at the first opportunity and enjoy the "lifetime fill" , ... following Jim's first links was my first clue that "non-silicone DOT5" even existed. Meanwhile I'll carry on as BK suggests.

 

Sorry Jim, it appears I've done you wrong. I don't know what this new fangled 'synthetic' fluid is, but if they say it works with ABS systems, I'm guessing it's not silicon based like synthetics used to be. Archer2's post seems like the definitive one as far as the 'older' style of DOT 3/4/5.1 is concerned.

 

I know this is an older thread.. but there is a GREAT advantage of Dot 4. It holds 200% more moisture absorbing capability. Dot3 is very old spec..
If you flush your brake system yearly- Dot3 is probably OK.

In vehicles with Dot 4, bi-yearly brake flushes.. I've never replaced a caliper, wheel cylinder or M/C. I use a vaccula or pressure bleed not to damage the M/C seals.

Michael