I have to add a bit of coolant (but i just use water, small water bottle) about once every week or two to the reservoir. i havent noticed any puddles, no steam, no white exhast smoke (and engine was torn down about 1 1/2 years ago) so i'm doubting its a head gasket. so i'm wondering where it could be going? it seems to dissapear faster when i've been driving harder. is it possible to have a pinhole rad leak or something that may only leak under certain circumstances? (ie high rpms?) i'm guesing my mix is about 80 water/20 antifreeze right now. is there any chance it could be evaporating somehow???