Believe it or not you probably need to clean the furnace. That means taking the burner out and removing the front covers and the combustion chamber so that you can get to the bottom of the heat exchanger. When these units get plugged up they run hot which puts a lot of heat back on the nozzle and the oil line heats up and expands forcing a small amound of oil out of the end of the nozzle where it drips back into the burner housing. While you have it apart take a mirror and a light and check the top of the heat exchanger for cracks which are very common with Miller furnaces. Be sure to use new gaskets when you put it back together.