I currently am driving a 2003 dodge dakota 3.9 liter v8 slt on 265/70/r16 tires and wheels, and i am averaging about 12 mpg city and approx. 14-15mpg hwy. im aware of at least one small exhaust leak near my catalytic conv. and i suspect that my fuel screen in the tank is either cloggged or needs to be changed. besides the obvious emissions check im in need of, what can i do to increase my fuel economy to 20 mpg or better on a $500-$1000 budget. also my dakota has 97,000 miles in the original motor and trans. i do regular oil changes as well since i purchased the vehile in december of 2016*

 

Put that $500-1000 into a small beater car and drive it instead. You won't get 20 mpg or better around town out of that truck.

 

To start, the 3.9L is a V6, not a V8. Second, your mileage seems horrid... Unless you're in a 4x4 crew cab and always in the pedal hard, you should get better than that, especially highway on the bigger tires.

I'm in a 98 regular cab with the 3.9L auto on 235/75/r15s and I'm getting 16-18 city, and 20-22 highway. Your first step is going to be a tuneup and all fluids. Cap, rotor, plugs, wires, good fuel treatment if you make short trips. Maybe a new coil since they're fairly cheap. If you never have, new O2 sensors all the way around for proper fuel trim, do NOT get bosch sensors. NTK or Denso are the ones you want. Pull your throttle body, just requires pulling the air hat, unhook cables, three wiring harnesses, and 4 bolts. Clean this up very good, make sure to pull the IAC off the back and clean that passage as well, do not move the plunger while doing so. While the TB is off, take a flashlight and look in the intake for any pooling oil, you may require a new plenum gasket, which can reduce performance and mileage as it's an unmetered air leak, and oil gets pulled into the cylinders. Get a new mopar pcv to ensure proper flow, cheap ones at parts stores are too weak.

None of these are expensive and are relatively easy to do, also be sure to check your tire pressure, 35 for cruising, 41 for hauling weight. Even with an auto trans, you should be getting at least 16-17mpg or so.