With 4.10 gears I am getting 15.5 mpg's out of mine. Gas is $1.95 here today and diesel is $3.15. I usually fill up after 450 miles. 450/15.5=29 gallons of gas at a total cost of $56.55. Assuming you get 20 mpg's out of your diesel and you drive 450 miles and then fill up it is 450/20=22.5 gallons for a total cost of $70.88. $56.55/450=12.6 cents per mile. $70.88/450=15.8 cents per mile. I would take cheaper to operate over a little extra driving range any day of the week. With a wife and 5 kids I'm lucky to drive 100 miles without someone needing to stop and pee anyways.

 

Well I don't stop at every gas station..

 

I had a 7500lbs trailer and the 5.4 did a decent good job, the diesel guys l-o-v-e-d to show off by pulling faster..
But if there are any hills, just floor it and hope for the best :-)

To be fair the 5.4 at redline actually sings really-really nice! Kind of like a mustang.