Well i filled up my brake fluid about 3 months ago to spec. but when checked the fluids the other day i could tell that i have lost some brake fluid. I know that you shouldn't have to ever fill the brake fluid (unless to bleed them or need some because of normal loss). There is no visible leak that I could find right now. The brake lines aren't rusted. I haven't pulled the wheels off yet (with it being too cold), but could one of the calipers be leaking or something? I haven't looked that hard into it yet because it hasnt been too big of a problem right now. Also, it seems as if I have to apply the brake a little more than usual, giving that spongy feel, so that gives me the reason to believe air is getting in the brake lines, therefore there is a leak/hole somewhere. Ideas? and how would I know if one of the calipers are bad, would i just see fluid, or is there another way to check them?