Synthetic Brake Fluid

[RIX97]

I'm doing a brake job on my 1998 Valk Tourer and wanted to top up my brake fluid. The manual calls for DOT 4 but I'm having a hard time finding any that is non synthetic since according to what I've read you can't mix synthetic with non synthetic and I was wondering if that is true. I like buying local but may have to check Amazon.

[Jess from VA]

From the web:  In most cases, brake fluids that are rated DOT 5 are the ones considered synthetic because they are made using silicone. Meanwhile, brake fluids such as DOT 3, 4, and 5.1 are the ones considered “non-synthetic”.

But then:  DOT 3, 4, and 5 are all synthetic. DOT 3 and 4 are glycol-based products that differ only by their boiling points (DOT 4 is slightly higher).  DOT 5 is silicone-based (also synthetic).

You cannot mix synthetic and non-synthetic brake fluid.  Most brake fluids that are DOT 5 or are silicone-based are considered synthetic compared to regular glycol-based brake fluid.  DOT 5 brake fluid cannot be mixed together with any kind of brake fluid and should only be used on its own.

It seems that one should avoid the term synthetic.  And one should avoid mixing Dot 5 with 3 or 4.

[RIX97]

From the web:  In most cases, brake fluids that are rated DOT 5 are the ones considered synthetic because they are made using silicone. Meanwhile, brake fluids such as DOT 3, 4, and 5.1 are the ones considered “non-synthetic”.

But then:  DOT 3, 4, and 5 are all synthetic. DOT 3 and 4 are glycol-based products that differ only by their boiling points (DOT 4 is slightly higher).  DOT 5 is silicone-based (also synthetic).

You cannot mix synthetic and non-synthetic brake fluid.  Most brake fluids that are DOT 5 or are silicone-based are considered synthetic compared to regular glycol-based brake fluid.  DOT 5 brake fluid cannot be mixed together with any kind of brake fluid and should only be used on its own.

I think I am more confuseder than when I started but thanks for trying to help 

It seems that one should avoid the term synthetic.  And one should avoid mixing Dot 5 with 3 or 4.

[Savage]

All brake fluid is synthetic, even if it doesn’t say it.
You’re looking for DOT 4.  Get a new can for the job.
DOT 4 is what should be in the bike already and you can add the new DOT 4 to that, although since you’re doing a brake job I strongly suggest you bleed and refill the front brakes, rear brake, and clutch with brand new DOT 4 fluid.

[WintrSol]

All brake fluid is synthetic, even if it doesn’t say it.
You’re looking for DOT 4.  Get a new can for the job.
DOT 4 is what should be in the bike already and you can add the new DOT 4 to that, although since you’re doing a brake job I strongly suggest you bleed and refill the front brakes, rear brake, and clutch with brand new DOT 4 fluid.

And the DOT 3 or 4 (sometimes DOT 3/4) that say synthetic on the container are just doing that for advertising. Replace the fluid every 2 (or fewer) years, and always from a fresh can, because it absorbs water from the air, which makes it boil at a lower temperature and turn brown faster.

[RIX97]

Thanks for all your help guys, I've decided to bleed the brakes and clutch.