Is DOT 4 Synthetic brake fluid OK?
 

That's what the label says.

I know DOT 4 is good. I know synthetic brake fluid is bad (not compatable)

I'm confused:confused:

Can anybody un-confuse me?

Synthetic fluid has longer life and is less prone to breakdown, flush total system and then add the fluid. I use Castrol synthetic DOT 4 and it has never let me down.

Like synthetic vs. dino oil, you either use one or the other. Like Gurkha said, flush the current fluid out before performing the transfusion...

I won't use anything other than Castrol LMA or MB brake fluid.

I tried DOT 4 synthetic once, and it left me with a spongy brake pedal. The local mcparts store doesn't carry it anymore due to the high number of complaints.

Funny you should say that, that's my problem. I've always used it but the new bottles say Castrol GTLMA Synthetic Brake Fluid , DOT 3 and DOT 4.

I think DOT 5 (the silicone stuff) is the fluid spec to stay away from. DOT 4 synthetic should be okay - I used it in my 300E and it worked great.

DOT 5 IS the Silicone
 

TonyB is right.

AND you have to replace EVERY rubber part in the system...First.

AND you have to "FLUSH" the system with Brake Cleaner...First.

BUT I would not attempt to "Flush" an ABS unit with Brake Cleaner , So I
think you're out of luck as far as DOT 5 is concerned.

DOT3 OR DOT4 are both fine...

"Mushy" pedal is air.