#4232, "RE: cant find dot 4 brake fluid for the life of me" In response to In response to 4 Apr-15-05 12:19 AM by MCubed45
umm mixing brake fluids is bad MMMKAY
stick to 3 like stock. HIGHER NUMBERS ARE NOT NECESSARILY BETTER. it's what your braking SYSTEM was designed for. i'll go dig up an article for you guys.
As a trailing note on the DOT ratings, if your car was designed for a particular type of fluid (especially prior to the development of DOT 4 fluids), you should make every attempt to stick with that fluid! For example, if your car was delivered with DOT 3 fluid, the internal components of the system (seals, brake hoses, and fittings for example) were specifically designed and tested for compatibility with DOT 3. Because DOT 4 fluids contain a different chemical composition, the system may not necessarily react in a positive fashion to the borate esters floating around in the mix.
In other cases, just the difference in viscosity of the two different fluids may cause the seals to wear at different rates. What starts as an annoying squeak might eventually become a torn seal or worse. The examples could go on and on, but the message here is this: it’s fine to upgrade from DOT 3 fluid A to DOT 3 fluid B, but you should think twice (maybe even three times) before switching from DOT 3 fluid A to DOT 4 fluid of any sort.
