? DOT 5.1 Brake Fluid (yes, 5.1)

[Jack]

Have seen newer DOT 5.1 brake fluid that is NOT silicone and can be mixed with both DOT 3 and DOT 4. DOT 5.1 costs about 3X-4X DOT 3.

Typical DOT 3 spec: DRY BP = 401°F, WET BP = 284°F.

Wagner DOT 5.1 spec: DRY BP = 500°F, WET BP = 356°F.

Seems 5.1 elevates BP a pretty fair amount ... a good thing.

I understand Silicone DOT 5 not recommended to mix with others, and water will puddle in silicone rather than mix. Wagner engineers don't like that.

I understand DOT 5.1 is factory fill on some newer brands/models.

Does anyone have real world experience w/ DOT 5.1 brake fluid?

JACK:gap

 

[JohnZ]

Jack, I seriously doubt if 5.1 is factory fill (at least on any U.S.-produced cars); DOT3 has been the industry standard for 75 years, and there are enormous potential liability issues with using anything else, in addition to the obvious cost issues. When I was the Viper Plant Manager from 1995-2001, the Viper owners asked me if I would change the factory fill from DOT3 to DOT4 to take advantage of the slightly higher boiling point, and it took almost a year of validation testing by Engineering before they'd release it for me, in spite of the well-known 100% compatibility with DOT3. As far as I know, the Viper is the only U.S.-produced car with DOT4 as the factory fill.