DOT 5.1 brake fluid

About to start the caliper rebuild. Does anyone have experience in utilizing the DOT 5.1 brake fluid? I am undecided between the DOT 4 and the 5.1(not silicon based I think). My entire system will be flushed, although I haven’t made my way to the fronts yet.

I went ahead and chose Dot4 synthetic. My brakes work great for regular driving, and it was much cheaper.

Advantage of DOT 5.1 is higher boiling point, lower moisture asorbtion rate, Longer life, lower viscosity so easier flow with antilock brakes and compatable with DOT 3 & 4 so you do not have to totally drain and flush the system. Price should not be an issue when brakes are concerned. DOT 4 will be fine, just not as fine.


I use dot 5.1 in my XJR as I use it on the track and fast (legal) road work, no issues, must admit I am not aware that it has lower hygroscopic properties than dot 4?

I researched 5.1 and unless I was racing, didn’t think it necessary. I’m eventually going to go ceramic front pads which I think will help keeping brakes from overheating, and thus not boiling the fluid.
It’s already a huge step up from original Dot3 non-synthetic to Dot4 synthetic.