these other guys are dead on. best ive seen in mine (z71 with 285s.) was 13mpg. average is about 9 to 11. you would be shocked at how much those 285s are killing you since im willing to bet you didnt regear for them...like i didnt. step back down to factory tires, shed some weight in the truck and keep the RPM under 2000. MAYBE 15-16 if youre lucky.
now another option would be instead of getting a honda or something like that, an old surplus crown vic. i know Georgia State Patrol is selling off their old ones CHEAP!! they just sold an 07 will 103k miles for 1300 bucks. i got 24-26 out of mine before the heavy mods. it still gets 18-22. big comfy and safe car too...
then like another said park the yuk and take the insurance off of it.
i know if money was an issue for me, the copenhagen would have to go. really got to weigh your vices and pleasures against your education. there will be plenty of time for fun and toys later, but this is your one chance at education brother, dont waste it!! worst comes to worst, sell the yuk, buy a nice fuel saver then when youre back on your feet good, shop around and get you a nice hoe already cummins swapped!