I am planing on bleading my breaks within the next few days. I bought a bottle of DOT 4 synthetic brake fluid, can that be mixed with the normal dot 3 thats already in there?

 

Interesting, I never heard of _synthetic_ brake fluid before but any DOT 3-4 should be compatible. Seems to me that if it really is synthetic, it would kind of defeat the purpose by diluting it with regular brake fluid-kind of like mixing regular and synthetic oil. It is DOT5 that is different stuff, It's silicone based and is not compatible with other brakefluid.

 

Mixing is fine, you just won't get any of the benefits of the DOT4 fluid. BTW, I have been told that all DOT3 and DOT4 fluid is actually synthetic. Haven't bothered to research it though. I like the Valvoline DOT4 from Autozone. Almost as good as the DOT4 ATE blue stuff but WAY easier to buy and cheaper, too.