Brake fluid

[tpanhuis]

Went to local bmw dealer yesterday and ask for Dot 4 brake fluid.He gave me GTMLA Castrol synthetic brake fluid.It says it is used in abs brakes and exceeds dot 3 and 4 requirements and can be used for all dot 3 and 4 uses---but does not say what specific dot this is..Dealer says this is all they been using the last 2 years.. Any one using this or familiar with product. TIA Ted

[Joe_C]

Only use the BMW brake fluid. The ABS unit is over $2500 and it's not worth the gamble of it not being compatible.

[Sailorlite]

BMW says to use DOT4, as I recall, with no specific recommendation for or against synthetic or a particular brand. Castrol can certainly make good brake fluid, e.g. their conventional "LMA", but I wonder whether synthetic fluid is a good idea for an RT that was engineered for before synthetic was available. And the synthetic fluids were engineered for current and future brake systems. Put another way, I don't know whether the "old" seals and hoses in your system are compatible with more modern synthetic fluids - not a safety issue but a leak issue.

[TomfromMD]

I understand that DOT 4 is glycol based and DOT 5 is silicone based. But what is the difference between "synthetic" and "non-synthetic" brake fluid?

 

Tom

[99Roadster]

The synthetic is fine. It's compatible with DOT 3 and 4. I've used it both the R and RT without any issue. The R has been getting yearly flushes for over nine years now.

[Twisties]

I don't claim to be an expert on brake fluid, but as a chemist I can assure you that glycols are synthetic. This wiki indicates all synthetic components. I suspect the "synthetic" label is purely marketing, and of no practical consequence.

 

Here is Castrol's MSDS . Quite a bit different composition from the MSDS cited in the wiki. Of course it only lists less than half of what's in it, by weight.

 

I just got BrakeBest Select DOT4 from O'Reilly/Checker. All they had. I can't find an MSDS, but wrote them for it. They are legally required to supply it. We'll see what shows up.

 

In the meantime, until someone tells me otherwise, DOT4 is DOT4 is DOT4 in my book. The Castrol product is in several of our bikes with no problems to date.

 

 

 

[Joe_C]

You can get the real thing at A&S Cycle for $4.50 / 12oz.