Brake Fluid Recommendations?

[Dan DiBiase]

My car's brake warning light has been flashing intermittantlyfor the  past week or so. I had noticed it when it was rainy for the past  several weeks (it would flash briefly, for may 30 seconds, then go  away) and had planned to have it checked out at the 35k service with  the dealer. Then, yesterday, while starting a drive home from Upstate  NY, it came on as I was rounding an entrance ramp to the NYS Thruway  and stayed on until I pulled over after about 10 minutes. I checked the  reservoir (why can't Audi make them clear so you can actually see the  fluid level??) and it appears to be a little low. The only thing  mentioned in the owner's manual is that the brake fluid must conform to  'FMVSS 116 DOT 4'. Will any DOT 4 fluid be okay? What do you all use?
  
  Thx
  
  Dan D
  '04 A4 1.8Tq MT-6
  Central NJ USA