DOT 5 mineral fluid is used primarily for racing, it is more hygroscopic than DOT 4 therefore needs changing more often so ok in a race car. I think the jury is still out on synthetic fluid, ok I suppose in a brand new system. I stick to my DOT 4 mineral.
Sorry, but think you have that the wrong way round; DOT5 is LESS Hygroscopic.
One of its main advantages for racing is that it has a higher boiling point.
