Well if your on disability then why do you have a work horse for a truck. If you where looking for fuel economy than a super crew f-150 with a 5.4l motor and 3.55 gears in the rear end was not the way to go. But that being said you are a little low on mpg average but only by about a 1.6mpg city difference. Only inexpensive mod would be a k-n filter. Other than that a high flow exhaust system $$$ and a rear end gear swap from 3.55 to 3.74 again $$$.