The brake fluid thing doesn't work that way. If it isn't a dragging caliper, most likely your bearings are going bad. when you drive (30 - 45 mph) can you notice any whirling noise that increases if you turn the wheel a little to one side or the other? That will put more pressure on the bad wheel bearing and give you indication that it is bad. Don't ride bad wheel bearings very long, they can score your hub which will then also need replacement and can in turn damage your CV shaft (all big $$$). If it is the bearing get it fixed quickly or pay lots more later.