DOT 4

DOT 4 is one of several designations of brake fluid denoting a particular mixture of chemicals imparting specified ranges of boiling point.

Additional recommended knowledge

What is the Sensitivity of my Balance?

How to quickly check pipettes?

Daily Sensitivity Test

In the United States, all brake fluids must meet federal standard #116. Under this standard there are three Department of Transportation (DOT) minimal specifications for brake fluid. They are DOT 3, DOT 4, and DOT 5.1.

DOT 4, like DOT 3 and DOT 5.1, is a polyethylene glycol-based fluid (contrasted with DOT 5 which is silicone-based). Fluids such as DOT 4 are hygroscopic and will absorb water from the atmosphere. This degrades the fluid's performance by drastically reducing its boiling point. In a passenger car this is not much of an issue, but can be of serious concerns in racecars or motorcycles.

As of 2006, most cars produced in the U.S. use DOT 3 brake fluid.

Boiling points

Minimal boiling points for these specifications are as follows:

Ingredients

One particular brand of DOT 4 brake fluid lists the following ingredients on its MSDS: