Dot 3 vs Dot 5 Brake Fluid

Quote:

---

I've used dot 5 in the Torana after building it all from scratch with new stuff....no problems and if you do spill it doesn't matter

---

Quote:

---

Also FWIW, despite the urban myth, your brakes will still work and your car will not explode spontaneously if you mix a little DOT 3, 4 or 5.1 in.


Dave

---

This guy was just topping off his car with some Dot 3, despite having had Dot 5 in it previously...

Quote:

---

dot 3 and 4 both produce water and eventually will rust out your lines/parts. dot 5 is silicone based and won't do that. if you use 5, you can ONLY use 5.

---

Quote:

---

Quote:

---

dot 3 and 4 both produce water and eventually will rust out your lines/parts. dot 5 is silicone based and won't do that. if you use 5, you can ONLY use 5.

---

produce water? they absorb moisture which can rust your entire system. the dot5 doesn't absorb moisture but i have read that since it doesn't absorb moisture that the moisture can collect at the wheel cyl and calipers. just bleed the system once a year and you should be fine.

---

the correct term is "Hygroscopic" which means that a substance readily absorbs moisture. Dot 4 (and the other polyethylene glycol based fluids) is hygroscopic and will absorb water from the atmosphere.....which is why you aren't supposed to use old fluid, particularly if it has had the lid off for some time. Moisture absorbed by polyethelene glycol brake fluid will rust all interior components of the brake system over time.

Dot 5 (not 5.1) is silicone based and will not absorb moisture. Since Dot 5 won't absorb the moisture, there is no danger of rust from water in the brake fluid, BUT any moisture in the system will tend to migrate to a dead end or high spot and rust in that area would then be free to form. Frequent use, bleeding or the use of stainless steel brake lines and components are methods of combating this corrosion.

There, clear as mud?

Dave

Quote:

---

Quote:

---

Quote:

---

dot 3 and 4 both produce water and eventually will rust out your lines/parts. dot 5 is silicone based and won't do that. if you use 5, you can ONLY use 5.

---

produce water? they absorb moisture which can rust your entire system. the dot5 doesn't absorb moisture but i have read that since it doesn't absorb moisture that the moisture can collect at the wheel cyl and calipers. just bleed the system once a year and you should be fine.

---

the correct term is "Hygroscopic" which means that a substance readily absorbs moisture. Dot 4 (and the other polyethylene glycol based fluids) is hygroscopic and will absorb water from the atmosphere.....which is why you aren't supposed to use old fluid, particularly if it has had the lid off for some time. Moisture absorbed by polyethelene glycol brake fluid will rust all interior components of the brake system over time.

Dot 5 (not 5.1) is silicone based and will not absorb moisture. Since Dot 5 won't absorb the moisture, there is no danger of rust from water in the brake fluid, BUT any moisture in the system will tend to migrate to a dead end or high spot and rust in that area would then be free to form. Frequent use, bleeding or the use of stainless steel brake lines and components are methods of combating this corrosion.

There, clear as mud?

Dave

---