I would like to get everyone's thoughts on the different types of brake fluid out there. I know there is conventional and synthetic, DOT 3, 4 and 5. I also know that there are a couple of different companies that has performance fluid made for them, like Wildwood. My question is what is really the difference between the different types of brake fluid on the market today. I will soon need to add fluid to my system and since everything is new I figured I need to start looking for the right product. In my case the car will never see the drag strip, it may see and auto-x event or even a road course. It will see a lot of street traffic and there will be time that the car may set.
Dot 3 is all you'll need. It's also good to flush the system to. You can't mix them. I don't remember what the differences is but but dot 3 will work well. And try not to leave the cap off for to long cause break fluid absorbs moisture from the air.
If you mix the two you will get a jelly mess. Seen it on a crotch rocket. not good. Definitely change the fluid in your system because moisture is your enemy. A vacuum bleeder works great. Use grease around the bleeder and vacuum line fitting to keep it from leaking vacuum. start with the wheel farthest away from the master cylinder and work your way toward it. Good luck!
DOT 3 & 4 are glycol/glycol ester based with DOT 4 having a higher temp rating. DOT 5 is silicon based and cannot be mixed with anything else. Unless you're doing some heavy duty autocross or roundy track racing, DOT 3 will do.
Dot 3 regular or synthetic...Both are fine, unless the brake component manufacturer recommends something else or you will be using it for severe service like frequent autocross, etc. More important than fluid type is routine maintenance. Best thing you can do to get long life from new components is to flush the system every 2 years by bleeding to push fresh fluid through the entire system. This pushes contaminants out and removes fluid that has absorbed moisture. Also, when changing brake pads, do not push pistons back in...it pushes contaminated fluid back up into the system, possible even into the master cylinder if pushed in enough. It is always best to flush with new fluid FIRST, then push pistons back in and change pads. This extends life of all the parts.
Well there is no need to bleed the system, as everything is new. So no one has any qualms about using synthetic?
Are the seals compatible with synthetic? I'm not sure if it even matters or not. Trying to think of things that might be an issue. Good luck!
New lines also? I've heard you could flush if needed. From what I've read, I'll stay with DOT 3/4. The glyco based stuff will absorb water (to about 3%) but the silicon stuff will not absorb moisture, which will isolate itself in the braking system and more rapidly cause internal rust. Just suggest you read some tech articles about using DOT 5. Some of the newer BMW's and probably others have DOT 5 from the factory, so it does have a use.
Not sure what you mean by no need to bleed as everything is new. I assume you mean it's all new and already bled? I am referring to maintenance down the road. Bleed the system every two years to replace the fluid with new as the fluid will absorb moisture over that time. Right now it's new so no need to do that. Synthetic is perfectly fine to use. It will not harm the seals at all and it will take more heat. The only time synthetic fluids hurt seals is when the seals are very old and need replaced anyhow.
DOT 3 or 4 is just fine. Like everyone else has said, it's hygroscopic and will absorb moisture out of the air. That's why you have to flush it every few years. DOT 5 can cause problems. Om pressure switches (old stuff with the round button brake light switch) it can eat the inside away and they will leak. Water will also collect at low spots in the system and in extreme cases, freeze. Rock hard pedal and no brakes. Just use a good name DOT 3 and you'll be fine.
