I have a 99 Saturn sl2 DOHC. The car has been losing oil, it isn't leaking anywhere and doesn't appear to be burning. I have to keep adding a quart about every 2-3 weeks. I just recently did an oil change, just oil. No coolant mixed in. I believe that it may have something to do with my head gasket or even with the engine block(I don't know that much about cars as you can tell) as the car has overheated once for about 3 1/2 minutes before I shut it off and let it sit overnight before I tried starting it again. The car isn't getting any heat. I need to replace the thermostat. Anyone have any ideas on what could be going wrong? I would like to trade it in and get rid of it but I cannot afford a monthly payment right now. Thanks for your help.