I have to ask why you think this is brake fluid? Coolant would be much more likely. What's it taste like?
It is normal for the fluid level in your brake master cylinder to drop over time. As the front brake pads
wear, the caliper piston extends farther out of it's bore to compensate, which lowers the fluid level in
the master cylinder.
For top-ups, any good quality DOT3 or DOT4 fluid will do, so long as it's fresh. I like the Motorcraft fluid,
or Castrol LMA. Do *not* use silicone-based fluid to top off.
Cheers,
Jeff Cook
'03 Marauder 300B, Dark Blue Pearl, Dark Charcoal/Flint interior, Badgeless front and rear, 4.10s and Lidio Tune