Hi guys, what the heck is the difference between DOT 4 and DOT 5 brake fluid... Never been into brake mods until now.

I just bought some DOT 5.1 motul brake fluid for my CRX, I still don't know what the heck this all means.



Thanks for your help.

 

i much much of a brake guy myself....but the "DOT"'s are somewhat of a rating system. the higher the number the higher the boiling point of the brake fluid, for racing situations etc. DOT 3 is what Honda Brake fluid is. I know that you can mix DOT 3 and DOT 4 brake fluid. But i believe DOT 5 is made up of a silicone base and SHOULD NOT BE MIXED WITH ANY OTHER TYPE OF BRAKE FLUID WHAT-SO-EVER!! Hope this helps??

 

Unfortunately DOT sucks at assigning designations. The DOT 5 is silicone and not compatible with other fluids, but DOT 5.1 is the latest synthetic which is compatible with DOT 3 & 4. Some vendors sell it as Improved DOT 4 just to avoid this confusion.

 

I dont know about Dot 5.1, but Dot 5 if used on an old system could leak. Dot 5 does not treat the seals like Dot3 or 4.

 

So Dot 5.1 should be good in an old 1989 CRX then????????

 

Will work great.. it is the best choice for a car that is driven.

 

Thanks. I appreciate your help.

Same goes for everyone. Thank you.

 

Chris - Are you still using Valvoline Synpower (DOT 3 & 4)? I've not noticed DOT 5.1 fluid at the local Discount Auto parts - is it only sold at specialty stores?

BTW, the stiffer Comptech front bar is the best thing that I've done to the car - I can now understand why there are so many people that raved about the Mugen bar.

 

No, the Synpower stuff worked ok (still used in the wife's car), but I found a deal on the Neo fluid, and I buy Motul when I get pads since Carbotech discounts it with a purchase. Both have higher dry boiling point so maybe I can skip the end of track day bleed often needed.

Yes, I think the larger front bar is an improvement but there have been some that do not like it.