Dot3, Dot4, Dot 5.1?

[brsvo]

Well I put new stainless flex lines on the front of my car and need to flush the old fluid out. I have forgotten the fluid I used last time what are the preferences.

[Mike S]

I use Motorcraft Dot 3 for my track car. Even the Porsche guys use it.

[brsvo]

Porsche guys using Motorcraft must say something! I seem to remember that Dot 4 is silicone and not good for the street (absorbs moisture?) Dot 3 is the standard in all cars what is 5.1 about?

[Meotchh]

DOT3, DOT4, & DOT 5.1 are all three glycol based, meaning they will "absorb water". Technical term is the fluid is hygroscopic. DOT 5 is silicone based so it is not hydroscopic. If you choose to run DOT 5 in a car that has always run glycol based fluid, you should perform a very through flush to remove the glycol fluid since it does not play nice with silicon based fluid & is very damaging if there is any moisture in the system. The other important difference in each is the boiling point.

Here's a little more detailed info I reference back to when needed...
http://www.advancepetro.com/differentbrakefluid.htm

Porsche guys using Motorcraft must say something! I seem to remember that Dot 4 is silicone and not good for the street (absorbs moisture?) Dot 3 is the standard in all cars what is 5.1 about?

[Mike S]

Porsche guys using Motorcraft must say something! I seem to remember that Dot 4 is silicone and not good for the street (absorbs moisture?) Dot 3 is the standard in all cars what is 5.1 about?

From my previous research, Motorcraft has the highest boiling point of all DOT 3 brake fluids that are not "race" rated.

[brsvo]

Thanks for the info I will do a complete flush of my system and run 5.1.