I have been noticing that i am loosing coolent in my car. The reservior tank is always empty in a week after i fill it up. I dun see any sign of leakage anywhere and i am not blowing smoke when i accelerate hard. The coolent is not chocolate milky color which means it's not the head gasket (correct me if i am wrong). However, i noticed that i was starting to overheat at the track (after 5 to 6 laps) the last couple times i was there. I am not overheating at all when i am driving on the streets. Any ideas???

 

you can slowly leak coolant into the combustion chamber via the headgasket, without it mixing with oil.