Brake fluid is a type of hydraulic fluid used in hydraulic brake and hydraulic clutch applications in automobiles, motorcycles, light trucks, and some bicycles. It is used to transfer force into pressure, and to amplify braking force. It works because liquids are not appreciably compressible.
Most brake fluids used today are glycol-ether based, but mineral oil (Citroën/Rolls-Royce liquide hydraulique minéral (LHM)) and silicone-based (DOT 5) fluids are also available.[1]
https://en.wikipedia.org/wiki/Brake_fluid?
| Dry boiling point | Wet boiling point[a] | Viscosity at −40 °C (−40 °F) | Viscosity at 100 °C (212 °F) | Primary constituent | |
|---|---|---|---|---|---|
| DOT 2 | 190 °C (374 °F) | 140 °C (284 °F) | ? | ? | castor oil/alcohol |
| DOT 3 | 205 °C (401 °F) | 140 °C (284 °F) | ≤ 1500 mm2/s | ≥ 1.5 mm2/s | glycol ether |
| DOT 4 | 230 °C (446 °F) | 155 °C (311 °F) | ≤ 1800 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
| DOT 4+ | 230 °C (446 °F) | 155 °C (311 °F) | ≤ 750 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
| LHM+ | 249 °C (480 °F) | 249 °C (480 °F) | ≤ 1200 mm2/s[16] | ≥ 6.5 mm2/s | mineral oil |
| DOT 5 | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 900 mm2/s | ≥ 1.5 mm2/s | silicone |
| DOT 5.1 | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 900 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
| DOT 5.1 ESP | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 750 mm2/s | ≥ 1.5 mm2/s | glycol ether/borate ester |
| ISO 4925 Class 3 | 205 °C (401 °F) | 140 °C (284 °F) | ≤ 1500 mm2/s | ≥ 1.5 mm2/s | |
| ISO 4925 Class 4 | 230 °C (446 °F) | 155 °C (311 °F) | ≤ 1500 mm2/s | ≥ 1.5 mm2/s | |
| ISO 4925 Class 5-1 | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 900 mm2/s | ≥ 1.5 mm2/s | |
| ISO 4925 Class 6 | 250 °C (482 °F) | 165 °C (329 °F) | ≤ 750 mm2/s | ≥ 1.5 mm2/s | |
| ISO 4925 Class 7 | 260 °C (500 °F) | 180 °C (356 °F) | ≤ 750 mm2/s | ≥ 1.5 mm2/s |
