I have used nothing but DOT 5 fluid in my Corvettes. Started when I replaced the calipers, and disks with Willowood parts. They only guaranteed their calipers to extreme temps (350+ degrees) with DOT 5. The DOT 3 or 4 is hydrophilic (attracts moisture like a day off) The "funk" that grows in the DOT 3/4 and makes it "dirty" is actually algae (no, not the same stuff as in your fish pond, but like it.) The silicone base lacks both the moisture, and nutrients to feed the plants. (the moisture is also the cause of corrosion of the steel parts, furthering the funk in the fluid syndrome) I have since replaced DOT 3/4 with 5 in all my vehicles. Some simple warnings though, be sure to completely flush the system (denatured alcohol was recommended by "Vette Brakes co.") label the damn thing so a half brained girlfriend doesn't put dot 3 in the system... they separate faster than Italian salad dressing. (another added plus of dot 5... it's harmless to paint, or our nice epoxy frame coating, and cavitates only under the most extreme temperature/vibration) More info is available from willowood, of Vette brakes company (cool sites too.) #2366