The only time I got 28mpg was from San Bernardino to Carpenteria, (just south of Santa Barbara CA) on-ramp to off-ramp, right to the diesel pump. It was raining lightly most of the way I never went over 67mph. I was only hauling about 750lbs. I average in winter 20mpg calculated, spring to summer I average 21mpg. This is mixed driving including So. CA freeway grid-lock at least once a week. See my signature for truck accessories.