I have a 2003 V6 Mustang with close to 150,000 miles and I am having problems. Lately the car has been drinking coolant. Literally the radiator and reservoir will be completely empty in a matter of 5 to 7 days. It also has been losing a little oil for a while now. This morning I started it and left for my normal routine and the car had lost all power. It just sputtered and wouldn't idle over 300-500 rpm's while in drive or reverse. It also makes a knock/shaking noise while in drive or reverse. While it is in park it sounds fine just a little gagging sound like it's dropping rev and stays at 900-1,000 rpm's, but once you put it in drive or reserve it drops the rpm rate down to 300-500 and won't hardly go. I have literally no idea where to begin. I have experience with VW's and some JDM's and normally it would point toward a blown head gasket. The car doesn't smoke except for a little bit when it first starts, and it has been doing that for quite some time. It is hard to notice the smoke and a lot of times it doesn't even do it. And I thought I saw some oil in the radiator, which is another indication in a blown Head Gasket, but I couldn't really confirm that and after checking the fluid it hasn't had any in it. Also, my girlfriend drove it about a week ago and the battery light started flashing while she was going up a hill. We recently replaced the Coil Pack, Alternator, and Battery within the last two years. Up until now the car ran fine, I had only noticed the loss of coolant when I had noticed I couldn't get any heat. After filling it up with coolant the heater worked fine. I'm at a loss here, and this is my only daily driver and my lively hood depends on it. If anyone has any info that could help me please let me know. I really appreciate it everyone.