What mods is require to achieve such mileage?

Can a SuperDuty auto 4x4 diesel achieve these kind of mileage? or is this just a Dodge myth?

 

my 04 6.0 4x4 cc will break 20 if I drive it nice, even broke 20 towing my popup toy hauler loaded with dirtbikes once by driving 60 mph, if I drive it with a heavy foot I get 18 hwy, 14 towing the hauler (off road popup/4 dirtbikes/2 canoes on top 4000lb), one time I got onl 13 @ 75 on flatland due to strong winds. mods are exhaust, airaide intake, accufab elbow, Egr and cat delete, hypertech programmer, dieselkleen centane boost, and ARE# shell, 285/75 tires, zoodad mod, duallies are geared lower and have more drag so drive even slowwer.

 

The best I have got is around mid 17 MPG. 20 MPG looks steep to me.

 

Drive any truck at 45 mph on freeway and you should get 20 mpg easily.
Even with V10

 

my 95 cc 4x4 long bed 5 speed w/3.55 not babied would get 18 mpg combined with 236k on the clock mostly stock. my 02 v10 has gotten a best of 12mpgs.

 

03 6.0 3.73 rears.17.90 empty at 70 mph 9.3 towing 14,000 at 65 mph.