If you've got hydrocarbons in the coolant you've got a bad head gasket, or even a cracked head. Last car I had that showed hydrocarbons in the coolant had cracks radiating from every valve seat. If it is the head gasket, it might not be blown yet, but heading that way.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.