Quote:
Originally Posted by Mart
Isn't dot 5 silicone? Some of the silicone stuff I have had has been purple.
If it is safe enough to assume it is conventional fluid, I always use dot 4 in preference to dot 3. I did some tests on a clutch slave cylinder years ago and the dot 4 was better.
Mart.
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DOT 5 is silicone and while it will be purple when new once in use the color can fade and it may appear clear or slightly amber. DOT 5 is non-hygroscopic meaning it will not attract moisture from the air as will DOT 3, 4, and 5-1. The water that can accumulate in brake fluid will cause corrosion in the worst case, but at the very least can reduce the effectiveness of your brakes as the boiling point of the fluid will be lowered. D-5 being silicone will not attract water, but it will hold microscopic air bubbles in suspension and cause what some will describe as a slightly spongy feel. D-5 has no potential to corrode your brake system, will not remove paint if spilled on the car, and will last a very long time. That can be a simple test for Heard. If you put some of your brake fluid on a painted surface, say a spot on the frame or a suspension component and it removes the paint then you will know it is not D-5.
With the primary difference being the boiling point I'm left wondering what difference D-4 made as compared to D-3 in your clutch slave.
I used D-5 in my coupe over 30 years ago and to this day see no down side, other than it is more expensive and yes, I do have a slightly spongy pedal.