Tech QuestionJohn Veatch, Houston, TX, 1956 Dodge Coronet 230 I have used silicone brake fluid since the late 70's. In fact it was so long ago, they didn't even require purple dye. I concur with everything you have stated in the past, I have both filled systems with it and topped off systems. In all cases, I can say my brake system sealing and corrosion probles virtually vanished. Now to my questions. What is the actual engineering reason ABS systems do not recommend this fluid? I have heard it is more compressible, but if so, that would defy the laws of physics stating liquids are virtually incompressible. If this is the reason, is it due to entrained air? Would pulling a vacuum on the fluid take care of this? Is this, in fact, a myth and the reason is more liability related? For years I have wanted someone knowledgeable to shoot straight with me on this, I turn to you for an honest answer... John- I think it has to do with viscosity. In my experience, most DOT5 is a bit 'thicker' than the standard mineral-based crap. This also explains why some guys have bleeding problems, air bubbles take a bit longer to gravitate up and out, and some GM masters have a very small compensating port, causing slow system refill. (Never been a problem on any Mopar). Correct: Of course, fluids are basically not compressible. I have also used it for about 35 years, but I don't use it in the new ABS cars. It might be fine, in actuality, I just haven't tried it. Rick
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