I have like a mix of water and oil in my radiator reservoir? does this mean cracked head or blown head gasket.?

This car is VW Passat V6 4motion. Thing is has sat in garage for about 7 months with no use was fine when went away now am back have this problem.I have like a mix of water and oil in my radiator reservoir? does this mean cracked head or blown head gasket.?
If someone put the wrong kind of coolant in it, it can turn dark %26amp; oily too.I have like a mix of water and oil in my radiator reservoir? does this mean cracked head or blown head gasket.?
sounds like you do have head gasket problem. check engine oil if it looks like milk then you surly have gasket problem.
the head is warped....you need to buy new heads...the oil is coming through the heads up to the coolant jackets and is mixing...buying and putting in new heads should take care of it

sunshine