My Airstream has been winterized for several seasons. Yesterday I opened the LP valves to utilize the heater. In doing so, an oily substance blew out from the stovetop area. It was clear, but had an odd odor. I would say there was about 2 tbsp of oily liquid that was discharged. What is it, and is it dangerous? I closed the LP valves and did not light off the system as it worried me. Does anyone know what caused that oily liquid to blow out?