1 - K&N won't do anything for city mileage, and I wouldn't run one anyway.
2 - Warm air is supposed to actually help fuel mileage. Don't flame me, flame the folks over on those super economy greenie forums. Anything that can be done for mileage, they've done it, and they either advocate leaving a stock intake or making some sort of warm air intake.
3 - Go over ALL the basics to get your motor in good tune (plugs, wires, cap, rotor, filters, O2 sensor, check cat...).
4 - Beware of gimmicky spark plugs.
5 - Nearly every time I've read of someone having a sudden mileage drop, it had to do with an old O2 sensor.
6 - Make sure your brakes are properly adjusted as brake drag is real and affects the lives or ordinary American drivers every day.
7 - The biggest factor for your mileage is your driving habits. As I mentioned earlier, there is a lot to learn from the nerds, uh *cough* folks at the cleanMPG type forums.

 

when the filters in the tank, its part of the fuel pump so no you dont replace it until your fuel pump starts going bad or the sender fails, the sender is what tells the gauge in the dash the amount of fuel you have.

in regards to the k&n being junk, its not a 'oh i get soooo much more mpg' but it does help better gas mileage and throttle response. its without question allows MORE air in, and more air in is better for the engine. an engine is like a runner with a straw in his mouth (paper air filter) take the straw out of the mouth (k&n air filter) the runner is able to breathe in more and run more faster and harder, just like an engine.

also weight is a BIG part of bad fuel mileage so people with larger tires, and junk in the trunk will usaully suffer with bad mpg

another thing to help gas milage is correct tire pressure and making sure oil changes are done reg.

absolutely!!! jeeps, older champions / newer NGK
bosch +2 +4 are junk.

 

Thanks for all the input and suggestions. I shall look into some of these things asap. I may go back to the factory air intake as I hate seeing that cone filter get so dirty so fast from the dirty water and road dust getting on it when it is wet. It`s a pain to clean and re-oil. I need to do my back brakes BAD as I doubt the previous owner did anything with them and now I`ve had it for 80,000 miles myself . I do carry a lot of crap around with me but all of it combined can`t be even 100 pounds. With warm weather coming I`ll have time to tinker with stuff. Still have my 4.5" Rusty's lift kit laying in the basement and most likely will never install it (Got it used but in good shape) might ponder selling it.

 

lift kit by itself may reduce your gas mileage on highway speeds. i'm almost positive that your bad gas mileage has SOMETHING to do with your O2 sensor. you tire pressure could be going down over time too. it is normal for vehicles to lose gas mileage over time, even though the engine and transmission is in great shape. your wiring starts losing insulation and obtaining cross interference between wires beside it.