REFLECTOR: Brake fluid

[Izzy Brownfield]

Sorry if this subject has already been discussed to death. Im new so i just have to ask. 
Whats the reason  or benefits of using dot 5 brake fluid ?  
It finally got cold (well somewhat) here in texas and both my cleveland brake pucks started leaking. Both "O" rings look ok just a bit less than round. 5606 is a tad thicker and might not had leaked. Another issue i have is the calipers came with nitrile "O" rings and Im not sure dot 5 is compatible. 
Should i replace with Nitrile or a different compound o ring

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