Peter M Posted 7June, 2015 Report Share Posted 7June, 2015 Someone asked last week about the best brake fluid to use. The advice given was to use a name brand of recommended Dot specification and change every few years. Here is a brief refresher post from a brake fluid "101" thread I came across that may interest some:Automotive hydraulic brake fluids used today are most often synthetic glycol-base, water-miscible fluids. Brake fluids generally have been blends of several components such as vegetable oils, various alcohol-based fluids, synthetic ester base oils, diluents and one or more oxidation and corrosion inhibitors. Blended hydraulic fluids have contained such lubricants as castor oil, polyoxyalkylene glycols, glycol ricinoleate, and glyceryl ethers of polyoxyalkylene glycols and such diluents as butyl alcohols, amyl alcohols, glycol esters, polyoxyalkylene glycols, monobutyl ethers, ethylene glycol monoalkyl ethers and the like.In addition to the myriad of synthetic base fluids (they can range from 7 to 11), brake fluids have anti-oxidants, corrosion inhibitors, and metal deactivators included.Not all blends have been entirely satisfactory in all cases. Those that are satisfactory with respect to most of the requirements are difficult to prepare, since a blend component that satisfies one requirement may be disadvantageous with respect to another requirement. Thus, a blend component that meets a high boiling point requirement frequently does not meet the low temperature viscosity requirement or a blend component that satisfies the low temperature viscosity requirement may adversely affect rubber parts used in hydraulic systems, e.g., cause swelling, softening, and the like.Brake fluid absorbs moisture form the atmosphere, thus it is hygroscopic. Moisture gradually reduces the boiling point, so the fluid should be changed periodically to remove water and other contaminants and to ensure the continued effectiveness of the braking system.The properties of different types of brake fluids are tested for many different characteristics such as PH value, viscosity, resistance to oxidation, and stability, and graded against compliance standards set by the United States Department of Transportation (DOT) as noted above.Brake fluid DOT specifications:DOT 2 is castor oil based; pretty much obsolete.DOT 3 is composed of various glycol esters and ethers.Boiling point: 284° F (140° C)DOT 4 is also composed of glycol esters and ethers, and boronic compounds.Boiling point: 311° F (155° C)DOT 5 is silicone-based. It is NOT recommended for any vehicle equipped with antilock brakes (ABS). It gives better protection against corrosion, and is more suitable for use in wet driving conditions.Boiling point: 356° F (180° C)DOT 5.1 is a high-boiling point fluid that is suitable for ABS-equipped vehicles. It contains polyalkylene glycol ether, but is more expensive than other brake fluids.Boiling point: 375° F (190.6° C)Even if they have similar base composition, fluids with different DOT ratings must NOT be mixedIf you are keen for more, the full thread is a good read and answered some questions like:Why is brake fluid deliberately hydroscopic?Why is brake fluid chemisty different between aircraft and cars?Why is Dot 5 not recommended for ABS?etc.http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3076040/1 Link to comment Share on other sites More sharing options...
Chris-p Posted 7June, 2015 Report Share Posted 7June, 2015 Good on you Peter. Thanks for posting this info. Oh I got rid of the double up for you Link to comment Share on other sites More sharing options...
Coastr Posted 7June, 2015 Report Share Posted 7June, 2015 OK...here's a question. I took some used brake fluid to the recycling place today but they turned me away with it and said they only took in engine oil. What's the best way to dispose? Link to comment Share on other sites More sharing options...
DS911 Posted 7June, 2015 Report Share Posted 7June, 2015 Thanks for the post Peter. Was planning on new fluid today actually and purchased some Castrol DOT4 in preparation. I really can't say why I picked the brand other than to use something I was familiar with. They were all similar in price, in fact the Castrol variety I bought was a touch more and therefore gave me some silly confidence it was slightly superior. Motul was about her brand that stood out at about 5 times the price of most others. Apparently it was a high temp - low degradation fluid suited to multiple track days. Anyway I'm sure what I bought is suitable for road use but I will revisit the discussion if I plan a track day. Link to comment Share on other sites More sharing options...
Peter M Posted 7June, 2015 Author Report Share Posted 7June, 2015 OK...here's a question. I took some used brake fluid to the recycling place today but they turned me away with it and said they only took in engine oil. What's the best way to dispose?Like you I've previously just added it to my waste engine oil and dropped it off at the local drop off points for recycling using the logic that there is already lots of nasty chemical compounds in used engine oil, what's a bit of brake fluid going to matter! I'll probably continue to use this approach for small incidental quantities.However for large quantities I think the more responsible approach is to save it up for the annual household chemical collection days that the local councils run in association with your state's environmental protection authorities like this one for example: http://www.epa.nsw.gov.au/managewaste/house-chem-cleanout.htm Link to comment Share on other sites More sharing options...
Peter M Posted 7June, 2015 Author Report Share Posted 7June, 2015 ...Motul was about her brand that stood out at about 5 times the price of most others. Apparently it was a high temp - low degradation fluid suited to multiple track days.... Darren, Until you mentioned brake fluid the other day I hadn't thought much about it even though I have done two pressure bleeds in the last year. My '85 specifies Dot 3 or 4 and my '94 specifies "Original Porsche Brake Fluid" which is Dot 4 and now compatible with 5.1 too. Consequently I just used a name brand Dot 4 fluid for the pressure bleeds. I guess if the Motul racing fluids are Dot 4 compatible, which they are, then they are viable for us and offer higher boiling points than the minimum Dot 4 specification.https://www.motul.com/au/en/products/oils-lubricants/rbf-600-factory-linehttps://www.motul.com/au/en/products/oils-lubricants/rbf-660-factory-line I hope someone with track day experience speaks up to say if there is a need to run special high temperature brake fluid or ordinary Dot 4 or Super Dot 4 for that matter, does fine. However I wouldn't be surprised if they tell us not to bother seeking solutions to problems that don't exist and say as long as our pads aren't too worn, the fluid is reasonable fresh and the bleeding has been done competently that's all we need to worry about! Pressure bleeders? Another useful topic to discuss maybe? Link to comment Share on other sites More sharing options...
tomo Posted 8June, 2015 Report Share Posted 8June, 2015 Great Infomation Thanks peter Link to comment Share on other sites More sharing options...
DS911 Posted 8June, 2015 Report Share Posted 8June, 2015 I hope someone with track day experience speaks up to say if there is a need to run special high temperature brake fluid or ordinary Dot 4 or Super Dot 4 for that matter, does fine. That would be good info. The sales guy where I bought the fluid said the Motul will go for multiple sessions but others like the Penrite 'race' fluid is really a one track day solution. Link to comment Share on other sites More sharing options...
Coastr Posted 8June, 2015 Report Share Posted 8June, 2015 Like you I've previously just added it to my waste engine oil and dropped it off at the local drop off points for recycling using the logic that there is already lots of nasty chemical compounds in used engine oil, what's a bit of brake fluid going to matter! I'll probably continue to use this approach for small incidental quantities. However for large quantities I think the more responsible approach is to save it up for the annual household chemical collection days that the local councils run in association with your state's environmental protection authorities like this one for example: http://www.epa.nsw.gov.au/managewaste/house-chem-cleanout.htm Ha! My council stopped doing waste pickup days of any sort. Don't even get the annual kerbsdie collections Link to comment Share on other sites More sharing options...
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