Richard, We started using ULSD in Seattle 12/04/04. I ran our fuel mileage numbers in 90 Thomas buses starting from 2/1/05 to today, and we get an appalling 5.4 mpg. Then I ran the same buses from 2/1/03 to 2/1/05 and they got an appalling 5.5 mpg. All 250HP C... Login to read more.