2013 Ford F250, 6.7 Diesel, Suggestions to improve mileage.

If I do mixed miles 1/2 and 1/2 highway and town I get about 14 empty if I do all in town driving which I seldomely do I get about 12. These big beasts are not much for around town. Empty going down the highway I can get about 17 mpg. Always about 12 towing 5th wheel or 13 or so with the TC. Of course mine is not a Ford but I think they all get about the same around that year.