I have to believe that the new ULSD fuel is definitely hurting my mileage. My "new" 04. 5 has 32000 miles on it and I always averaged 17mpg empty until my local filling station changed fuel last month. Now I average 15. 5 empty. My towing mileage also dropped from 12. 5mpg to only getting 10mpg on my recent trip last week(2000 miles on I-95) I tow a 10000lb 5'ver and never go over 70mph while towing.