while getting an oil delivery my whistle is dripping oil ? Home heating oil delivery

While the oil delivery guy is filling my inside tank at the intake outside of the house, the whistle drips oil. The whistle is still working just dripping oil. In the past the delivery guy just held a rag there while filling. This time I had a new young driver and he stopped filling my tank. I called the company and a guy came out and checked it both inside and outside the house and found no sign of any other leak. He said he will tell the driver to come back and fill and hold a rag there while filling but I'm not sure how experienced this guy is either. It seems there should be an answer.