DOT 5
DOT 5 is one of several North American designations of automotive hydraulic brake fluid, denoting a particular mixture of chemicals imparting specified ranges of boiling point.
DOT 5 is a silicone-based brake fluid (contains at least 70% by weight of a diorgano polysiloxane[1]).
Unlike polyethylene glycol based fluids, Dot 5 is hydrophobic.[2] An advantage over other forms of brake fluid is that silicone has a more stable viscosity index over a wider temperature range. Another property is that it does not damage paint.
Using DOT 5 in a DOT 3 or DOT 4 system without proper flushing will cause damage to the seals and cause brake failure. DOT 5 brake fluid is not compatible with anti-lock brake systems. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.
Boiling points
Minimal boiling points for these specifications are as follows (wet boiling point defined as 3.7% water by volume):
| Dry boiling point | Wet boiling point | |
|---|---|---|
| DOT 3 | 205 °C (401 °F) | 140 °C (284 °F) |
| DOT 4 | 230 °C (446 °F) | 155 °C (311 °F) |
| DOT 5 | 260 °C (500 °F) | 180 °C (356 °F) |
| DOT 5.1 | 260 °C (500 °F) | 180 °C (356 °F) |
| DOT 4 | Brake fluids | DOT 5.1 | ||
|---|---|---|---|---|
References
- ↑ Standard No. 116; Motor vehicle brake fluids Code of Federal Regulations, Title 49 - Transportation, Chapter V - Part 571 - Federal Motor Vehicle Safety Standards (49CFR571), Subpart B, Sec. 571.116 Standard No. 116; Motor vehicle brake fluids
- ↑ http://auto.howstuffworks.com/auto-parts/brakes/brake-parts/types-of-brake-fluid.htm
- ↑ FMVSS 116