Low Viscosity Brake Fluid Importance?

[Ruofdez]

Did a brake fluid change only to realise after that Dot 4 might not be good enough. Apparently Dot 4 Low Viscosity is required.

How important is this and do I need to be doing another fluid change to get the right stuff in or is the Millers Dot 4 I used likely to be fine?

Searched but nothing on the forum about it.

Thanks.

 

[Ruofdez]

This is what I used

https://cdn.opieoils.co.uk/pdfs/millersoils/BrakeFluid-Dot-4.pdf

 

[MJJamieson]

Low Viscosity is for ABS ESC etc. So yes I believe you should.

 

[Ruofdez]

Low Viscosity is for ABS ESC etc. So yes I believe you should.

Damn. Looking at the spec the viscosity of the Millers stuff I used is only marginally more than some of the low viscosity stuff however maybe that’s enough to make a difference. Maybe I’ll see if I can find the viscosity specs for BMW stuff to see how far from that it is.

Looking at other threads I think there are a lot of people that aren’t running low viscosity fluids so if it is important hopefully this thread will be useful to people searching.

 

[MJJamieson]

I use this from Euro, don’t know if class 6 is for low viscosity?

 

[Ruofdez]

I use this from Euro, don’t know if class 6 is for low viscosity?

Viscosity of that at -40F is 700. What I used is 750.

 

[Ruofdez]

Here’s a description I found for some low viscosity stuff that explains why it might be important:

The BMW DOT4 ESL brake fluid is a low viscosity formula for modern ABS and DSC systems. BMW recommends low viscosity brake fluid for all chassis beginning with the E60 5-series. Low viscosity (LV) is a thinner fluid that works better than a normal fluid in the small channels and passageways in the ABS/DSC pump. Using the heavier fluid will result in a delayed response to ABS and DSC activation and a spongy feel in the brake pedal (only during ABS stops). BMW ESL is a DOT4 rated fluid and is compatible with other DOT3 or DOT5.1 fluids. For track use, a heavier high performance brake fluid such as Ate Typ 200 or Motul RBF600 or RBF660 is recommended because of their higher boiling point and because the thicker fluid will thin out at track temps. But for street use we recommend switching back to a LV fluid, especially in colder climates.

 

[mmm-five]

The figures for that fluid don't seem much different to the figures for DOT4 fluid from Castrol, Fuchs, Motul, Gulf.

Can't find the spec/tech sheet for the BMW fluid - which is a bit stupid of them when they want to crow on about how their fluid is better for your car than others.

+100ºc

• Millers - 2.32
• Castrol - 2.3
• Fuchs - 2.3
• Motul - 2.5
• Gulf - 2.6
• Shell ESL - 2.1

-40ºc

• Millers - ?
• Castrol - 1200
• Fuchs - 1400
• Motul - 1750
• Gulf - 1700
• Shell ESL - 675

 

[Ruofdez]

The figures for that fluid don't seem much different to the figures for DOT4 fluid from Castrol, Fuchs, Motul, Gulf.

Can't find the spec/tech sheet for the BMW fluid - which is a bit stupid of them when they want to crow on about how their fluid is better for your car than others.

+100ºc

• Millers - 2.32
• Castrol - 2.3
• Fuchs - 2.3
• Motul - 2.5
• Gulf - 2.6
• Shell ESL - 2.1

-40ºc

• Millers - ?
• Castrol - 1200
• Fuchs - 1400
• Motul - 1750
• Gulf - 1700
• Shell ESL - 675

Thanks for putting that list together and I agree re BMW. 750 to fill in your blank for Millers

I'm thinking the marginal viscosity difference with what I put in will be fine, certainly until the winter.

 

[biojo]

Ive used

https://www.eurocarparts.com/ecp/p/car-accessories/engine-oils-and-car-fluids/auxiliary-fluids/brake-fluid/?524770150&0&cc5_179&type=shopping&gclid=Cj0KCQjw19DlBRCSARIsAOnfRejN1-W7KJWkdE3EEnTTpxuTTfjmtZQocqTrOWgllx7he5LqQ16YDaEaAonZEALw_wcB

no issues