Over how many weeks have you been checking it? I many times fill within 30 miles of home. Then before we leave again top the tank off from a gas can. I have seen many times where I top off and the next time I check it, it will take more gas. Sometimes after filling I move the unit 2 or 3 feet and can dump in another gallon or two. I sort of figured after filling there is still air in the tank after a few days the gas displaces the air and i can get more in. I've found many times after a station fill I can hand fill from a can 10 to 15 gallons. Don't know just saying.
