my camaro has coolant that looks like choclate milk in the entire cooling system including the resivoir and in the upper and lower radiator hose. when i drained the coolant it looked like it was a mix of antifreeze and oil. When i bought the car it was sitting for at least a year and a half that i know of and the guy i bought it off of only ran water in iteven in the winter. So far that has cost me a heater core and a freeze plug. what could cause this? i've never seen any thing that looks like this before. Please help!

 

It could be a lot of rust in there, you said the previous owner just ran straight water. No telling when it was last flushed properly. Check your oil, If it looks milked with white foam in it then you probably have a blown head gasket. Worse case scenario is a cracked block.