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DOT 4 user here. Never spilled a drop on paint, by accident anyway. Never had a fluid related problem. To me DOT 5 tries to solve a problem that doesn't exist.







Same here, I run ATE DOT4 Super Racing Blue in my brake systems and hyd clutch set ups,...DOT5 is the preferred fluid for the collector/show car because it doesn't adsorb water, and being silicone based has an added advantage of a slightly higher boiling point than that of DOT3 and DOT4 fluids, and prolonged storage/non use makes it user friendly to the system...however DOT5 while not absorbing water/moisture, does absorb oxygen, which over a period of time makes the fluid aerated with micro air bubbles, causing a "spongy" pedal...

DOT4, is of the Glycol base, which puts it temperature operating wise, in the middle range of petroleum/mineral base DOT3, and Silicone DOT5, DOT4 is the preferred fluid for high performance braking systems, or systems that will see boiling points reached for extended time periods (as in road racing, or HP driving), where as DOT5 when nearing it's boiling point, if oxygen entrained, will diminish the line pressure in repeated braking, hence not often used in a performance braking system,...downside to DOT4 is it will absorb water, although at a much slower rate than than DOT3 fluids, there are modified DOT4 fluids, such as ATE Blue or Gold, that have higher/finer properties than "standard" DOT4's, but the costs are much higher, but the performance results are higher....

So, IMHO, DOT5 if your building a trailer queen, or garage ornament, showcar, anything of that nature...

DOT4 Racing fluids if your concerned with high/repeated performance braking use, and are using the car for it's intended purpose

I've run the gambit of fluids from DOT3 to DOT5 over the years, and while I like the paint protection that DOT5 offers, it pails in comparison to the repeated performance usage of modified DOT4's, anyone who's brought a braking system's fluid up to it's boiling point, and for extended periods will understand...

Mike