I am from the Texas area, I had a customer with simular problem. After going round and round with the local LP supplier we finally had them replace all the old tanks with new aluminum tank and the problem disappered, we feel the tanks were holding left over oil previous fills. One of the biggest reasons for the excess oil is due to the temperatures the engines are running at, it causes the oil to "crack" out. The older systems were running cooler there for the oils stayed suspended and burned off in the combustion process. All these changes were made to clean up the emissions.