DOT 5 Analysis Results

[Mark L.]

The attached file contains the analytical results, visual observations and conclusions regarding the tests on 4 samples of DOT 5 brake fluid. While there does not seem to be a smoking gun here there clearly is a relationship between a sample that had claimed poor empirical performance and the visual appearance of the sample. I think many will view the report as helpful in selecting a brand of DOT 5. If someone wishes to conduct analysis of other types I can provide test samples.

[Gary B.]

Re: DOT 5 Analysis Results

[Patrick B.]

Re: DOT 5 Analysis Results

Nice job Mark on this objective comparison. The various fluids from the 90's to present don't show much variation. Even though the quality of the Johnsen fluid seems poorer than the other fluids, the idea that DOT-5 fluid had changed over the last few years appears to be false.

[Joe L.]

Re: DOT 5 Analysis Results

The attached file contains the analytical results, visual observations and conclusions regarding the tests on 4 samples of DOT 5 brake fluid. While there does not seem to be a smoking gun here there clearly is a relationship between a sample that had claimed poor empirical performance and the visual appearance of the sample. I think many will view the report as helpful in selecting a brand of DOT 5. If someone wishes to conduct analysis of other types I can provide test samples.

Mark------

One thing that I have noted using DOT 5 fluid for a long time is that the color of the fluid changes over time from a rather deep purple to a yellow. I believe the purple color is a dye rather than the fundamental color of the fluid, itself. Dyes may change colors over time for a variety of reasons.

[Owen L.]

Re: DOT 5 Analysis Results

Thank you so much for taking on this part of the DOT 5 question. In the process, I learned a small bit about FTIR as I was unfamiliar with the test and have a few clarifying questions:

What might account for the overall lower line of sample D compared to the others?
Does the test show that all of the samples are using the same chemical formulation?
How might the coloration of the fluid affect the test?

[Mark L.]

Re: DOT 5 Analysis Results

Owen, thank you for taking the time to read this. According to the lab chemist the variation in the curves among the samples suggest water is the variation with sample D having the greatest amount. Remember that silicone fluid is not hygroscopic, which is why we like it, and we can see the amount of water is very small but I'm surprised we see any at all. No other chemical differences were noted.
The coloration to me suggests "something" is different with D. In fact I believe D would not pass the DOT 5 spec due to the color and D was problematic when used in the brake application according to Ken.
I don't believe the color changes significantly with age based on my experience. I can tell you sample A is about 30 years old.

[Owen L.]

Re: DOT 5 Analysis Results

I don't believe the color changes significantly with age based on my experience. I can tell you sample A is about 30 years old.

Mark, My '67 has had DOT 5 since getting stainless bore calipers in the mid/late-'80s. I've never flushed the system but do check it at least every year. The reservoir level hasn't changed much at all - I don't ever recall adding more fluid - and it's still a full-on purple color. My '72 had regular DOT 3/4 when I got it in '90 or so and it went into a long unplanned storage for 30 years. When I started working on it at the start of the pandemic, the caliper bores were crystalized, chunky, and the pistons were pitted but thankfully the master had drained out. What a mess. Putting on new Lone Star calipers and wanting the same performance I've gotten from my '67's brakes, I put in DOT 5 in spite of the warnings everywhere. I like to live life on the edge and so far so good.

[Ed D.]

Re: DOT 5 Analysis Results

Mark,
Did Lonestar indicate that the sample D, they supplied was a new product ,or was it a used sample from a failed caliper. Was it a brand name product?
Ed

[Mark L.]

Re: DOT 5 Analysis Results

Ed,
When I asked for a sample that had caused leakage problems no one was either willing or able to provide one to me. That was a surprise I was not expecting. I then spoke with Lonestar to ask if they had one and they sent me a sealed container of the brand they knew to cause problems.

[Joe L.]

Re: DOT 5 Analysis Results

Mark, My '67 has had DOT 5 since getting stainless bore calipers in the mid/late-'80s. I've never flushed the system but do check it at least every year. The reservoir level hasn't changed much at all - I don't ever recall adding more fluid - and it's still a full-on purple color. My '72 had regular DOT 3/4 when I got it in '90 or so and it went into a long unplanned storage for 30 years. When I started working on it at the start of the pandemic, the caliper bores were crystalized, chunky, and the pistons were pitted but thankfully the master had drained out. What a mess. Putting on new Lone Star calipers and wanting the same performance I've gotten from my '67's brakes, I put in DOT 5 in spite of the warnings everywhere. I like to live life on the edge and so far so good.

Owen------

I'm very surprised that your DOT 5 fluid remained purple in use. I used several different brands over the years and all turned yellow in use. I recall the first DOT 5 fluid I used MANY years ago was supplied by Stainless Steel Brakes Corporation in Clarence, NY. They were the ones that sleeved my original calipers. Later, I used other brands when I removed the calipers for one reason or another.

I do still have a sealed, gallon container of DOT 5 manufactured by Dow-Corning. This is at least 25 years old. It remains fully purple. So, time, alone, apparently does not result in a change in color.

[Gary B.]

[Ed D.]

Re: DOT 5 Analysis Results

Color intensity declines over time and if exposed to UV light it will accelerate the deterioration. We use make samples of perfume bottles ,with no real perfume fluid in the bottles, for display in drug store window. The fluid was ethylene glycol and color matched with dye to match the real perfume color. . After a year in the window the samples were returned for refurbishing. The fluid was almost clear. I would not be trying to color match DOT 5 from different manufactures with time and environment variables in play.

[Gary B.]

[Terry M.]

Re: DOT 5 Analysis Results

The Dow Corning fluid I used in my 1970 turned clear in the master cylinder. I can't imagine how it would have been exposed to UV in service. Exposure to atmosphere maybe, but even that is limited but not impossible. I haven't opened any of the containers in several decades, so I don't know how that dye is holding up in the sealed metal containers.

[Joe L.]

Re: DOT 5 Analysis Results

As I mentioned previously, this fluid is at least 25 years old and remains originally sealed.

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