Synthetic brake fluid???

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4spdragtop

4spdragtop

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I have never used synthetic brake fluid, can anyone tell me the pros/cons??

Also what would be recommended for 67 cuda factory standard front disc and rear drums/

thanks
4spdragtop
 
Dot 5 won't absorb moisture over the winter layup period. I switched to dot 5 afew years ago and have not touched brakes to this day. Downside was they took alot of bleeding on the back small air bubbles get into the fuild so don't shake the can. Save some money and buy quart can for change over as I used most of it by the time I was done. I would do again.
 
It's supposed to be less resistant to water I believe, I don't like it though. I went through the brakes in my car and completely bled the system of old fluid and used it. I will be going back to regular fluid.
 
I have used DOT 5 silicone brake fluid in all my non-ABS cars for 20 years, without a hint of rust. Most claims against it are bizarre and unfounded. The best defense is that the U.S. military uses it. When I first bought it, the auto parts guy said "you must get every trace of old brake fluid out or bad things will happen". Total bunk. The only problem with leaving old DOT 3 (glycol) fluid is that will leave spots that might rust and not get the benefit of silicone. I have always done the change when replacing wheel cylinders and hoses, and after flushing the tubes. The one downside is that silicone has a slightly lower boiling point than brand new glycol fluid. That is why road racers use glycol. In practice, glycol fluid soon absorbs moisture, resulting in a lower boiling point, so the regular driver is better with silicone.
 
Can't say more than BillGrissom, he's took the words right out of my mouth. I have owned several vintage and antique cars, and used in every one without any issues. Best thing since disc brakes.
 
So does Dot 5 come in either silicone or synthetic?? Dad has DOT4 here that is synthetic??

Thanks
4spdragtop
 
I bought a gallon of silicone fluid years ago from a Hemmings ad. Always used it in new, clean systems with no old brake fluid. Love it. No rust; everything looks brand new upon disassembly. My original stash was running out so I got some Dot4 recommended by a parts counter guy. Just before using it, I thought I'd mix a little of my silicone (which I've since learned is Dot5) with the Dot4 in a clear glass. The result was something I don't think any of us would want in our cars! The two remained liquid but clearly did not mix. So, I bought some Dot5 and it mixed perfectly. Each had a purple color. I googled 'Brake fluid' and learned a lot about the stuff. You should do the same...
 
4spdragtop said:
So does Dot 5 come in either silicone or synthetic?? Dad has DOT4 here that is synthetic??
Click to expand...
I think all DOT 5 is silicone. You could call it synthetic since it is man-made. I don't know what synthetic refers to in brake fluid. Is there is a natural source for glycol fluid? The distinction is usually for hydrocarbon oils. Some are natural ("mineral", from the ground) and others are man-made in chemical plants. If one separates components (distillation) or even chemically changes them (cracking), they are still called "mineral". I guess "synthetic" means combining smaller molecules to make the final product (synthesize). While researching that, tell us what Techron really is.
 
DOT 5 is silicone, he asked about synthetic specifically. Its what i use, valvoline dot 4 synthetic. Best bang for the buck. Silicone has major issues with air entrapment making for a soft pedal, the pro side is it doesnt absorb water so corrosion in the system is non existent..
 
Stormy69, you didn't tell us what "synthetic" brake fluid means. I poked around and couldn't find an industry standard definition. It appears that all fluids stating "synthetic" are DOT 4. The reverse is not assured since DOT 4 does not specify the material, but only a standard for properties like boiling point and moisture absorption. To get DOT 4 rating, glycol fluids require additives, which is what "synthetic" probably refers to. I suspect it is more a marketing term.

DOT 5 is a superior rating, and originally only achieved by silicone fluids. However, some glycols mixtures now meet that rating, and are termed DOT 5.1 to distinguish from silicone. Confusing? Since glycol, DOT 5.1 fluids can still rust your brake internals and require flushing every 1-2 years.

My pedals are very stiff with DOT 5 fluid. I have never seen any bubbles in the reservoir. I don't shake the bottle, and I pour it down the side of a funnel, which you should do with any brake fluid.


In my reading, I found that silicone brake fluid is used in very cold climates like Finland and Russia, which seems to disagree with bizarre claims that silicone can be bad because any water can separate and freeze, causing plugs in the brake lines. How does this water get in the system? Glycol fluids suck it in from the atmosphere. I also read bizarre claims that silicone can degrade seals in older brake systems. Hard to believe since it is a pretty benign substance. In counter to that, I read that 50's British racing cars used silicone and that glycol fluids would degrade their seals.

Addendum

In more poking, I hit the mother lode. See http://adlersantiqueautos.com/articles/brake2.html
A few excerpts:

I called Valvoline and asked which part of the formula was synthetic. The reply was that these glycols are not naturally occurring molecules, so they are synthetic. Emphasizing “synthetic” seems to be a marketing technique rather than unique chemistry.

Paint will still blister upon contact with SynPower® brake fluid. Have a water bucket and sponge ready before starting brake work to immediately dilute and wipe up spills.

Even with its anti-corrosion package and low-moisture-absorbing formula, Valvoline still recommended changing brake fluid every two years, which it felt was about the frequency of brake repairs on vehicles driven daily.

I found other sites that said "synthetic brake fluid" is Valvoline marketing hype. There are no "mineral" brake fluids. It is like selling "inorganic water" or "organic charcoal".
 
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