oktx

I'm sure its never been changed, so it's time. Does synthetic vs non synthetic matter?

Tron Z

Best practice would be not to mix and match brake fluid types. If you wish to use synthetic, buy a little extra and thoroughly flush your system.

Vader_C5

I used Amsoil DOT4 last time for my C5.

Dads2kconvertible

You can mix them without issues if that's what you're asking. Synthetic usually means you can go longer between changes but that varies based on your use case.
Look at your clutch fluid too since you say the brake fluid has probably never been changed. If it looks like oil change that too.
And be prepared to change your master cylinder soon. The piston sometimes builds up some crud or rust just past where it usually stops moving. When the pedal goes to the floor many times during a bleeding process that crud/rust pushes past the seal and can start leaking.

spfautsch

Technically speaking, all dot3 and higher brake fluid is synthetic because the molecules have to be chemically cracked. Dot3/4 are both polyethylene glycol which is derived by polymerizing ethylene oxide (the primary ingredient in antifreeze). The two can be mixed safely - the primary difference is fluids with a 4 designation have higher boiling points. Should not be mixed with mineral oil based fluids.

Dot5 is a silicone-based fluid with an even higher boiling point. Also technically synthesized. Absolutely cannot be mixed with mineral or poly-glycol based fluids.

The "synthetic" moniker is mainly a marketing tactic that engine oil producers latched onto in the 2000s. I'm not a fan of Amsoil, but here's a really good write-up on what the term "synthetic" means.

https://blog.amsoil.com/are-all-synt...vs-v/?zo=34396

Supercharged111

Don't forget about 5.1, here's a blurb from Valvoline.

Brake fluid DOT 5.1 uses glycol ether and borate ester compounds but has an enhanced performance like the silicon-based DOT 5. We can say that it is a non-silicone version of DOT 5 but compatible with DOT 3 and DOT 4 types of braking systems and fluids.



With that said, racing fluids seem to be DOT4 just like racing pads rarely exceed a mu rating of F, despite there being more highly rated street variants out there that don't perform as well as the tra k stuff.

Beast

If you ever plan on doing an HPDE, you can use hawkHP600, you can use it for the street and track. I use it. Synthetic vs non synthetic, I don’t think it matters.

spfautsch

Again, the point of my chemical explanation is that it's all synthesized. Ethylene oxide is a gas, which is produced through a chemical reaction and is then mixed with other chemicals to produce numerous other compounds such as:

Polyethylene glycol = dot 3 / 4 brake fluid
Ethylene glycol = antifreeze

Propylene is a close cousin to ethylene, and when hydrated becomes propylene glycol = used as the base for most eye drops

In short, it's not refined from dead dinosaurs at any stage of it's existence. Therefor it's all synthetic. Buy the one that has the highest boiling point regardless of whether the container has the word "synthetic" on it.